[1] Okay, so (as I thought) you are comparing a twenty year old game with some notion you hold for the game, a hypothetical standard, and not against other games, and much less against contemporary games. Yes, you are correct, the game is flawed. It is to the credit of Ion Storm that you think so highly of the game that you are disappointed it was not a virtual reality (on a pentium).
[2] Well, your point is valid. I would counter that the RPG elements may be a bit clunky from a roleplay perspective, but they add another dimension to the gameplay, nonetheless.
Engendering a choice, creating the opportunity to customize a playthrough, so that one might improve Denton's ability to fight or hide, or even a little of both (radar transparency but no silent running, for instance) makes the game deeper and affords more replayability. Just like the augmentations, which require a choice in potency and specificity ([e.g.[/i], a drone to spy or an anti-missile defence: how far away from Denton?) the ability to adapt and prioritize a particular ability give greater agency to the player.
So it wasn't perfect; the point was that the implementation sparked other developers to create better games, once they saw how the implementation worked — and didn't.
But the critical factor that created such an impact was giving the player more agency.
[3] The whole point is that, in a single game, the player can choose to be a tank or a ghost (or a compromise somewhere in between). In a single-player, character-based profession-facilitated first-person perspective.
I'm curious to know if there is any game that you think has implemented stealth well. Did you like Thief, for example? Did you think it was a better implementation? Having both games (actually, all three Thiefs) I much prefer to sneak around as Denton than Garrett. YMMD.
[4] Exactly. The game has a synergy of all the gameplay styles available and, depending on the investment of RPG equity in offence (like marksmanship with a rifle versus a rocket-propelled gun) and defence (like stealthy silent running or radio transparency) the player can act with better or worse constraints.
The sheer range of options is appealing.
There is nothing to prevent a stealthy Denton from a toe-to-toe fight (apart from the injuries!) so, as you say, the incidental decision that a particular bad guy needs to die horribly painfully can be accommodated. Joy is burning a mook with chemical weapons, and laughing while they run around in a circle screaming! Or pepper spray to the face with a follow-up clubbing to knock them out: "Sit down and shut up!"
edit: clarity

[2] Is there some way the XP system might be improved to your liking? What I meant by my comment was the primitive RPG XP reward was akin to the augmentations, allowing a, say, "soft" skill incremental part to the "hard" nanotech augmentation upgrade. I haven't played the latest games; how do they implement it in those?

[2.1] This is a much more productive investigation: Why was the sequel not as good as the first game?
I really wanted to like the sequel. I completed it a couple of times. I think the last moment of play I had was when I was trying to sneak past a robot dog, which was patrolling up and down a single line, in a tiny rectangular space. It failed, critically, to suspend my disbelief. Stealth was silly, in this context; but mainly it was fiddly. I'm less fond of the timed button sequence to solve a conflict than I was decades ago. (I grew up playing platformers, like Donkey Kong.) And blunt force is difficult for a stealth build.

I would play (and had played) past such moments, but the game seemed — empty? Pointless? Repetitive?
(Aside: I would like to be able to play Hitman, but my PC is too weak.) :(

Because of the limitations of the console, all the levels were tiny areas. More than this, though: All of the missions were simple. Critics unkindly said it had been "dumbed down". (Simplified ammunition, which you liked, others thought prevented them from exercising their inventory management skillz, for instance; it didn't bother me, though, as the accumulation of ammo for the weapons I don't use in the first game becomes mildly irritating, too, easily counteracting this.)

Perhaps if they scaled the whole interface down, so that the characters were half the size they went with, or smaller, then the exercise might have been more successful? Or link more different areas together, so that (back-tracking!) all the puzzle pieces weren't in the same loaded zone? (Not necessarily contiguous areas; but not necessarily linear, either. It's a tricky balance, to be sure.)

Unfortunately, back-tracking, too, was made more irritating than the simplified puzzle piece retrieval; part of my disquiet was the silly unrealistic floating of the characters. As if physics had been subverted, or the game took place on the Moon, or in the Marianas Trench. (I wonder how it plays on a modern PC.)

[3] Didn't you know? Those shades that JC Denton wears are a pair of Joo Janta 200 Super-Chromatic Peril Sensitives! (His bionic eyes can see right through them, of course, but enemies can't see him, because they believe that if he can't see them, they can't see him. :)

Hmm. I guess what I like about the obviously-not-even-close-to-realistic crouch-stealth concept is the simplicity. Sure it lacks realism, but I don't enjoy having to switch between a half-dozen modes, via touch-typing, in the middle of a fire-flight. (I rarely play Real Time Strategy games.) The crouch-down / stand-up status is determined by the Control key, conveniently located left and right, for either fifth digit to manipulate. "Realism" is a secondary consideration, as long as it doesn't break the suspension of disbelief by being inconsistent, since pressing the button on a mouse is nothing like pulling the trigger on a firearm, or laying a mine, or throwing a grenade.
Again, it seems (like targeting intermediation, vide supra), what I like about the game is what you dislike?

I found the narrative compelling. I wanted to see what would happen next. I wanted to see what each augmentation did, to me and against opponents. To experiment with the alternatives. The sequel quashed this urge.

I also really liked the "open-world" approach to each level. France, to me, is the best set of levels; Paris and the castle (after the linear chateau) allow the player to determine how to solve the various conflicts: brutally or subtly, from above, below or along the ground. For a long time I played as a ghost, almost inevitably using all my darts quietly removing opponents (especially those who didn't know they were on the "wrong" side, just following orders: It yields a sort of socially just chivalrous smugness ;).

Again, I'm not sure what went wrong with the sequel, but it didn't compel me the same way. The tech was improved. The characters (potentially) interesting, but clumsily developed. The story is still relevant.

I think they tried to balance the game too much, perhaps. Each mission always had a stealth option and a hacking option, naturally, but were simply different doors to the same room, and resulted in the same rewards. (Compare with the submarine base that one could swim to in the first game.) As well, there seemed less flexibility, since it was harder to use alternate solutions counter to the upgrade path the player had chosen. So it was both formulaic and inflexible, with tiny zones of activity.

And there was no granularity to rewards to compensate for the fiddly interactions; if there were, say, a sliding scale for XP rewards based on the alert level or total fatalities, it would have been much better. (And would have uncontroversially improved the first game, too.)

Interestingly, I first played the sequel as the demo that was released to magazines (and online). And the demo, I thought, was much superior to the actual game, when I played it. The demo had cherry picked useful upgrades and provided an interesting scenario. I think it, ironically, demonstrated what was wrong with the game itself. :D

There are two models: one in which the player tells the avatar what to do, and the avatar carries out the actions autonomously, with skills and rolls affecting their effectiveness. The other is one where the player carries out the action. Deus Ex is the latter.

You can still model the effect of skill with aim speed, steadiness, speed, spread, recoil, reload speed, maybe even damage (although I'm not a huge fan of skill based damage modifiers on firearms.. it's the same bullets and same gunpowder that deals the hurt). Deus Ex does most of this but the way aim is implemented is just.. poor. The effect you get for lacking mastery is way, way too exaggerated to make it fun or smooth. I can't imagine anyone thinking that, arbitrarily, having to stand still for half a minute before you can pull the trigger is fun or makes the game flow better. And I don't see how it would help people with disabilities. How does it help? You still have to aim and hit the target. The "stand still for half a minute" aspect of it doesn't make it any easier. Mechanically it's you, not the avatar, who has to aim and pull the trigger. I know people who basically quit Deus Ex over the first level. And the developers themselves extended the demo by adding the NYC mission after they realized the first level just doesn't show off what the game has to give. It feels way more static and linear than the more urban areas of the game; NPCs are there to stand around and tell you what to do or give you items to help you along the way, but it really feels like a "final tutorial mission." Which, from story perspective, is what it actually is. The first mission, on an isolated island, where your performance on the field is evaluated.

The gameplay is heavily tilted in favor of stealth because you can't have much skill in different weapons at this point in the game; you don't have many weapons; you don't have much ammo at all to begin with; you don't have armor or augs; you don't start with weapon mods. This, I think, is what turned a lot of people away from Deus Ex. They tried to play it like an FPS, and the game kinda gives you the idea that it might play like an FPS, but then the first mission smacks you in the face. Aim is slow and piss poor, you have a couple magazines of pistol ammo which you can easily spend up in the first firefight if you don't stealth-headshot through it (and with the aim, it's really difficult to headshot in an open firefight), bodies give you a bullet or two (if not crap like darts).. add to this the turrets & the robot, and you have a scene that can't really be played like and FPS. So it's a long and slow mission, and even those who like the non-fps parts of the game, well, NYC proper has much more to offer.

[i]
gameplay is heavily tilted in favor of stealth because you can't have much skill in different weapons at this point in the game[/i]

LOL, stealth. A beginner to the game wouldn't know, but once you got pass Liberty Isle and read the "anti-walkthrough"(or watch a zero-kill gameplay video), you will realise that you can just run through most of that level and use that GEP Gun to blow up any door that gets in your way. All you really NEED to do is run up the statue and talk to the terrorist leader. Everything else is just a distraction. Btw, the GEP Gun is seriously a better "stealth" weapon than poison darts on a crossbow.

Yes, the AI and game design is broken. But exploiting its flaws is so much FUN AND HILARIOUS.

You try to pull the same tricks in DE2, and the enemies will quickly shoot you to death. But that's probably because DE2 enemies were designed to have better aim even on easy mode, and the small narrow level designs make it hard to find cover or hide.

[1] The GEP gun (read: Rocket-Propelled explosive / Grenade launcher) is almost as fun to use as the flame-thrower. Watching your immolated enemies run around screaming never gets old.
[2] I suppose this comment relates to your first assertion, that the GEP gun is a stealth weapon. Otherwise the hyperbolic "game design is broken" statement is intellectually dishonest.
[3] You are referring to the the horrible sequel, not the recent ones? Yes, there were some improvements in the game between the first and second iterations. The claustrophobic levels were a complete turn-off for me. It almost seems like the capture the flag strategy (as you implied: get to the statue and talk to the leader) from the first game was deliberately circumvented. Now that game's design was broken.
No question the process of aiming is different, (and, specifically, not particularly beneficial for those with disabilities). I would question your strict definition for Deus Ex; pretty much every game has additional factors in combat. (Quake was so popular because the game specifically does NOT muck around too much with the combat mechanic; a heavy gun might take longer to load and fire, but there is almost no recoil, IIRC, because it is surprisingly complex to model the physics, so the developers just ignored it, and the game works because everyone is equally better/worse off.) Like a lot of the game, the combat was an attempt to design a better mechanic. It obviously isn't perfect, but I wouldn't say it's broken. What players encountered in the well-meant design may have been the impetus to design later, better combat mechanics: "like Deus Ex, but …".

Again, specifically, the intention is to make the game compensate for the skill of the avatar as manipulated by the player. Not the best design, but, not the worst, either. I wouldn't last a New-York minute on a Counterstrike server, yet I can beat Deus Ex using stealth and (a lot! of) patience.

There aren't a lot of factors to play with; increasing delay between reticulated targets, and shortening the precision period, are two useful ways to mesh the need to make combat vary for avatar skill with the temporal constraints of the underlying game. Stealth is all about timing, after all, and a further complication (like waiting for a bull's eye in an exposed position whilst sneaking into a covered area) leverages the game's existing proscenium to incorporate gaming aspects that are otherwise difficult to model and incommensurate.

I've been playing through Tom Clancy's Splinter Cell, again, because I do actually like the stealth mechanic when it is done well, and this game I think is excellent.

To use your dichotomous model, the player tells the Fisher to, say, pick up a body and carry it somewhere less conspicuous, a task that is modular and cannot be interrupted (though it is fun to select his weapon and watch him drop the body like a sack!). Yet, again like Deus Ex, the game also allows for direct interaction (shooting his weapon and its various attachments, like the sticky camera).

What Deus Ex lacks is a light meter that indicates the ambient darkness which surrounds JC. Both Ion Storm's Thief and the Ubisoft franchise implement a light meter. Fisher also has an infrared filter, which allows for dark vision. It's nice to have a third-person perspective, too, to allow the player to see around the avatar; this is plausible as Fisher can move his head control his glances. The addition of the mouse-wheel to control avatar groundspeed is brilliantly ergonomic.

You made the point that running and gunning the first level is difficult because all of the game features are absent (augmentations and their levels, advanced munitions, surplus ammunition, etc.) which in fact induces the player to stealth. This, I would argue, is working as designed. Could the implementation have been smoother? Sure.

I think one of the best areas in the game is the stealth section of the tutorial.

I like Deus Ex 1, though I would not play it today without the GMDX mod.

As for the shooting, Deus Ex uses the Unreal Engine. Just play the game Unreal from 1998 and compare the shooting to Deus Ex, no idea how they managed to make the gunplay so much worse in DX.

I'm not bothered by the XP and skill system. Though I prefer the Praxis system that's used by DX:Human Revolution.

Deus Ex is arguably the most overrated game sold on GOG. Not only it is overrated but it is objectively bad on most aspects.

Gunplay is awful. Stealth system is poor. Level design is weak. Story is uninteresting. Art style is dull. Soundtrack is barely decent.

Its a product of it's time and even then, I wonder if it was truely that good back in the days. Considering that Half-Life came out in 98 and was superior in every aspect, I dont see how it managed to become successful.

Just this weekend I watched my little sister play Deus Ex for the first time, with GMDX. She's got the light meter. I honestly don't think it makes much of a difference. I can see it helping in a few situations, e.g. when you you get the lighting glitch that is caused by clawling up too close to a wall and you suddenly seem fully lit even though you're in a pitch black area, or in some areas where the world might seem darker than the game considers it to be.. but no, I don't think the light meter was ever something Deus Ex really needed. Perhaps, if they made the lighting play a larger role. I feel the Splinter Cell series has more deliberate lighting and I would actively look for shadows in it. In Deus Ex, it just feels.. a part of the world, nothing more, nothing less, a backdrop that sometimes comes handy, but in many areas you just go with what you have and don't care much whether it's dark or not.

I agree fine speed control in splinter cell is pretty nice. I don't like the third person at all. For me it kinda takes away the thrill and kills the immersion. Same problem in Hitman. Otherwise cool stealth games, both of them. I think the design was supposed to be "play as you like it". I've seen a lot of people get turned away from Deus Ex because they think you can play it as a shooter, but the first level plays absolutely terrible if you try to play it as a shooter, so they're in for a miserable experience. So if that's the design, it's a terrible mission.

If the design goal were to induce you into stealth, it *kinda* works but I still think it's a little boring mission. Pretty much any mission from the first third of the game could induce you into stealth just as well. But I think some others would be more exciting. And evidently the developers thought so too, since they decided to release the second mission for the demo after its initial release.

De gustibus non disputandum est.
Yeah, I can see how just adding a photometer wouldn't work (it would need some coded interactions on a deeper level in the game, not just another attribute for the PC, like being wet or bleeding). As you say, the more deliberate shadow play in Splinter Cell, because it was implemented better, makes for a better stealth game.

Actually, after I wrote my response I played a bit more and decided that what I liked most, unlike the Thief series, for example, was that Fisher can take out an opponent at close range (silent subdue), thereby not losing the stealth advantage automatically if spotted. Obviously one character can't take out an army in a toe-to-toe fight (which would be silly and not fun), but this mechanic allows for a more graceful series of failure states, so that one might end the level with little health and few munitions but still successfully.

Third person is an interesting debate. What is lost is the proprioception. When one is walking, the position of limbs is within the regnance of consciousness, but in a game there is no way (yet!) to transmit this (kinaesthesia) awareness to a player. One knows the state of balancing on a beam by the forces felt on the body, and particularly the feet (though shoes impair the perception).

Thus I prefer third-person sometimes, even if I agree that first person is generally better. (There's a great level in The Nameless Mod where one must descend into a subterranean mise en scène, but it relies on stepping across many columns of rock, some of these vertical strata are of such small dimension that they are only large enough for a single foot, and must be navigated by jumping, like a true platformer. Anyway, obviously chosen by the fan-developer/s purposely, it is incredibly difficult because of the first-person perspective. That and, if one has chosen to allow a local helpful troglodyte the access to talk — necessary for other problem solving — bursts of irrelevant dialogue on such topics as how to best cook rats will interrupt the process, at key moments. This is funny, but only the first time; after that the uninterruptible jump-scare dialogue is just irritating. :)

I understand the game, I know what makes it amazing, and it is still a great game, but I do feel the winds of age haven't been kind, and it's clunky as all heck.