Those can sometimes be useful, as long as the game is balanced around making them useful. Basically, either they need to work consistently, or enemies not immune to them need to have enough HP to not die easily.

An example of a game that got it right, at least for a portion of its battles, is Final Fantasy 3 (FC); in random encounters, status ailments work really well, so your black mage can easily disable the enemies (as long as you don't run out of level 1/4 MP); unfortunately, status ailments don't work at all in boss fights. Final Fantasy 3 (DS and derived versions) is an example of a game that handles it poorly; status ailments hardly ever work (well, the time I got the Sage job early with the help of a glitch I was abie to put enemies to sleep with Shiva, but that would still not always work, even when she decided to use her sleep attack).

In Dragon Quest 2 (FC), some enemies are dangerous enough that you will want to status affect them. In the remakes, most enemies aren't as dangerous, and the Defeat spell seems less reliable (both for you and against you), while Firebane/Explodet are stronger, making status ailments less attractive (though casting Stopspell on those golden batboons who can wipe out your party with Sacrifice when at low HP is still a good idea).

I'm reminded of another thing; I prefer it when enemies have limited MP just like your party members. Final Fantasy 2, Finan Fantasies 5 through 7, and SaGa 1 do this, while Final Fantasies 4 and 10 (at least 10's Dark Aeons) and SaGa 2 do not. (In SaGa 1, enemy attacks have limited uses just like yours; if the enemy has no attacks, it will either run away (if a random encounter, including a certain (supposedly) invincible one that uses boss music and gives the boss death animation when it runs away), or just keel over and die; it's too bad SaGa 2 doesn't do this. (Also, in SaGa 2, no fair that a certain robot can toss nukes at you while your own robots can't; as its single use is cut in half, rounded down.)

Edit: One other thing I forgot to mention: In FF6, in the later part of the game enemies have so much MP that reducing it to 0 is not a viable strategy. This is in contrast to FF7, where enemies (even bosses) have lower MP totals so the 100 MP drain from Magic Hammer can run enemies out, and to FF5 where there are a few abilities (Magic Hammer being one of them) that do percentage based MP damage, making it viable to reduce even high MP bosses to 0 MP.

I think magic should be like described in Discworld, you can't do anything with magic that you couldn't do normally. Magic is just another way to do things. Else it usually is overpowered compared to other things. Most games fall in this pitfall and make magic a lot more powerful so you have no choice but play a magic wielder. Which is not bad in itself. I just wish there would be sometimes more balanced games. Mass Effect was nice in this area, you could mostly play the game with a fighter just as you would with a Mage (in this case it was "biotics", still a type of magic)

Magic is so much more than just damage spells.

It can be used to heal, to buff, to create area-of-effect status boosts and nerfs, to create temporary fighting units, to summon permanent-until-dispelled units, to aid or hinder travel, to enchant weapons, to directly attack the enemy's mana pool, to dispel existing spells, to immobilize, to hasten, to intimidate, to take control of some of your enemy's forces, to persuade shopkeepers to give you a better deal, to pry into locked doors and chests without setting off traps, to detect cursed items, to disenchant or remove cursed items that you didn't have the wherewithal or foresight to check first, to see in the dark, to hide in plain sight... and maybe even to do extra damage by matching the type of attack to the enemy's weaknesses.

Of course, if you insist on ignoring the multi-tool in favor of a sledgehammer, who am I to stop you?

In fact, I find that damage is the most boring effect that special abilities can have. (It's one issue with Final Fantasy 7; look at the summons and limit breaks; there's way too much of a focus on damage; also, weapon techniques in SaGa games fall into this pitfall (though at least spells don't, except in the SaGa 3 remake)).

Also, don't forget intended item duplication, as is found in some Might and Magic games. (Yes, there's a way to duplicate items, and yes, it is clearly intended by the developers.) Ultima 6 also has a spell to duplicate items, as well as a bunch of other fun (though often useless, or only good for what one might consider an exploit) spells, like turning items into creatures; there's even a spell that removes all creatures from the game except the Avatar and Lord British (along with a way to softlock the game with that spell).

Even Pokemon has more variety in its moves than just damage; Growl, which lowers the enemy's Attack and is available at the start, is just the tip of the iceberg. *uses Baton Pass*

Another interesting thing Elder Scrolls related:

* In Arena, there is a rather interesting class called the Sorcerer. While other spellcasting classes recharge their spell points by resting, Sorcerers do not; instead, Sorcerers need to use their innate spell absorption to absorb spells cast by enemies in order to get the SP to cast spells. (Or you could just drink Potions of Restore Power, of course.) As a trade-off, Sorcerers get more SP than any other class (3x INT, while Mages get only 2x INT), and they can equip every weapon, as well as armor up to chain mail, but no shields for whatever reason. Note that Sorcerers need high WIL, as that stat is important for their spell absorption.

* Daggerfall, unfortunately, broke this strategy, as the Spell Absorption advantage seems to only work against your own spells; also you can take 3x INT as SP and Spell Absorption without the disadvantage.

* Battlespire fixed Spell Absorption (though there is a now enforced rule that you can't absorb a spell if it would put you over maximum SP; Arena's manual mentions such a rule, but the actual game Arena doesn't actually work that way); the Daggerfall situation otherwise applies, except that there's no resting. (The unable to regain SPs disadvantage prevents you from using items to restore your SP, and it prevents you from also taking the Regenerate SPs advantage, though you can still take Spell Absorption.)

* In Morrowind, classes no longer get innate traits; instead, the traits formerly associated with the Sorcerer class are now associated with the Atronach birthsign. It is possible to absorb spells cast by summons, as well as temple blessings; it's also worth noting that spell absorption is no longer WIL dependent.

* Oblivion is like Morrowind, though the inability to regenerate SPs is a more serious disadvantage (since resting is no longer required for non-Atronach characters). The Atronach SP bonus is now a constant effect rather than an increase in SP multiplier. Interestingly enough, some enemies, including Vampire Sorcerers, have this birthsign. Also interesting is the fact that the Ayelid Well's effects are coded in such a way that they can't be absorbed; then again, this is probably a good thing because you probably don't want to absorb the Restore Magicka effect in the first place if you can't regain SP on your own.

You could also fall on the water from a high height, not take falling damage, try to walk on water, and then take the falling damage you would have taken earlier had you not landed in the water. Ouch!

depends on setting, I think? Coz I've almost forgot about this restriction, since I rarely see it nowadays.
On other side - I remember some fantasy books (offtop, but still), where magic was the only way to deal with heavy armored "tanks". Thats where this idea regarding ignorance of armor came from.

but physical fighters usually have similar sorts of skills too, no? (for comparsion with ice - stun/slow mechanic. And when it comes to fire's DPS equal - something like bleeding)

out of curiosity - are you talking about western FF3, or eastern FF3? Coz I've played both, but it was quite a while ago to remember mechanics, based on your description (still loved them tho. Actually, classic FF franchise was one of the things to inspire me for this thead.

thats kinda what I thought of. Just like: fire damage can be both caused by fireball, or flamethrower. Or, in order to heal somebody, medic can use both bandages/potions/other medicine or holy magic. But then there comes question - what s the point of using magic at all? Thats why, in my opinion, it should have some special feature, that only magic may have (but nothing OP, to make physical characters unviable).
For example - as I've said in original post, ability to ignore armor. BUT at cost of reduced damage (physical attacks will have more powerfull flat damage, which make such characters best at killing hordes of garbage monsters. But their damage can be negated to zero, if enemy has lots and lots of armor - thats where mages will shine). In theory, yeah - coz in practice it may reduce the need to have physical DDs on bosses. Just grab a tank and bunch of mages, who will constantly spam their spells (which will ignore all boss'es defences) - and boom, your party is unstoppable.
So - maybe make magic not ignore armor completely, but penetrate some amount of it? (like 50%) In my opinion, resource type shouldn't declare your specialty. E.g - usage of magic shouldn't restrict you to be a support (there may be lots of different progression ways - to heal and buff friends, to curse and debuff enemies. And yeah - to deal damage too)

I am talking about the game that was released under that title in Japan, and later remade for the Nintendo DS; said remake, which did see overseas release, changed the game mechanics, and in particular made status ailments nearly useles for the player. (On the other hand, the DS version did make the Bard job useful, so there's that.)

The "western" FF3 you're thinking of is really Final Fantasy 6; in that game, I didn't use status ailments much (except for using Edgar's free confusion attack), but there are instances of status ailments working on bosses; with that said, if you want to hit bosses with status ailments, Final Fantasy 5 is a better choice.

By the way, some of the FF games have some rather interesting approaches to magic; FF2 (spells get stronger with use; some of the best spells are instant death attacks (if your equipment doesn't interfere with it) and single target Berserk), FF7 (magic comes from Materia; does suffer the problem that normal battles are too easy for support spells to be useful there), FF8 (draw magic from enemies; problem here is that you'll junction spells to your stats, and casting the spells will reduce the bonus to the stat you get from the junction).

Personally, I like having diversity of damage formulas; it may make things harder to balance, but it makes the game strategically much more interesting.

For example, in SaGa 2 (using Final Fantasy Legend 2 translations here):
* Some weapons simply do damage based on STR, AGI, or MANA, mitigated by enemy defence, provided they hit. (Balance issue; AGI is needed for these weapons to hit; all STR means you miss all the time, whil all AGI lets you do tons of damage with AGI based weapons.)
* Some weapons do fixed damage, but are mitigated by enemy defense. Cannon-type weapons (including SMG and Grenade) work like this, and hit an entire group of enemies at once. There are also single-target guns and bows that work like this. (Note that the Samurai Bow actually behaves like a cannon.)
* Martial arts attacks do damage that increases as durability decreases; the final attack additionally does triple damage. The attacker's stats have very little effect here.
* Spells typically hit a group (some hit all enemies), and are mitigated by the target's MANA. Note that this is percentage based mitigation, unlike physical attacks which use a variant of ATK - DEF.
* Multi-hit physical attacks exist, but except for one rare drop (from a special endgame enemy that could be considered a superboss) such attacks are only found on monsters. There's also a physical attack that is effective against everything (always hitting and ignoring defense), but it is only found on one particular enemy and on one particular rank 11 monster that does not appear as an enemy. (Note that monsters are available as party members in this game, so you can use these attacks yourself.)
* Laser Gun does 351-400 damage to a single enemy regardless of defense and resistances. Missile does 200-400 damage to all enemies. NukeBomb does 400-600 damage to all enemies. There is no way to mitigate the damage done by these weapons, but often other attacks do more damage.
* The final boss has an attack that hits your entire party for 99-639 damage (in the original version); there is no way to mitigate this damage. (Notice that the range is rather wide here.)

Speaking of interesting formulas, that definitely brings The Spirit Engine series to mind. Quoting my reviews:

SE1:
"For example, how does 22 + 3S + 0.23S * 0.5P + 1.66P, where S is skill level and P is party level, sound for merely determining a character’s base health? Or how about the Spook Summon priest skill, which costs 2 mana, takes 5.5 seconds to cast and summons a ghostly creature that will remain on screen for 0.48S + 0.12P + 17.2 seconds (unless it’s cast by the one priest who’s unfamiliar with the spell, in which case the duration is reduced to 0.4S + 0.12P + 16 seconds), which creature will attack enemies every 4.68 seconds with Holy Bolts that have a base damage of 2S + 0.66P + 6 unless a party member’s health drops below 4 + 0.2P, in which case it’ll heal said party member for 1 + 0.2P instead of attacking?
I sure hope you’re not confused already, because you’ll have to keep these things in mind if you want to develop your characters properly and not need to grind in order to make it to the end of the game. You’ll also have to keep in mind the damage type of each skill, because enemies have vulnerabilities, resistances and immunities which you’ll need to account for during battle, some even having abilities that will temporarily change their attributes."

SE2:
"Now the formula used for all but three active skills, and also for health, has a set form. That form, if you’re curious, is ((XS + YPS) * (82 – S)) / 82 + ZP + N, where S is skill level, P is party level, X, Y and Z are the factors, which vary from skill to skill, by which these values are multiplied, and N is a number, which again varies from skill to skill, added to the result. In case of active offensive skills which use a weapon, the weapon damage, multiplied by a number which again varies from skill to skill, is added at the end of the calculation as well. Passive skills have a much simpler formula, though along the same lines, while the three active skills that do not follow the same pattern as the rest may be expressed as N + XS – ZP. And no, I didn’t get any signs wrong, so this is all very interesting once you realize what it means.
With me so far? Good, because there are also five different damage types and the corresponding defensive values associated with each of them, which values are split into resistances, expressed as a percentage, and armor, expressed as a set value deducted from the portion of the damage that makes it past the resistance. And then you have chi, which acts as a shield against all physical damage until it is depleted, aurora, which does the same for magical damage, and dodge chance.
[...] Nearly every creature you’ll face will differ from the others, not only in appearance but also in attributes and tactics, so you’ll need to correctly choose the skills to use in every situation. And the choices aren’t limited to the up to 24 different skills you’ll have available at any one moment, but also include the ability to have the characters wait, individually or as a group, either for the right time to strike or for their energy bar to charge enough for them to enter overdrive, which grants massive bonuses for the next action.
[...]
To give a few examples, you’ll face enemies that can’t be hit while they attack and others that can’t be hit unless they’re attacking, enemies that constantly regenerate and others that constantly lose health but heal themselves whenever they strike, or enemies that attack harder the more they’re hit and enemies that stop attacking to greatly increase their defenses and rapidly regenerate when they’re badly injured. And let’s not even mention normal abilities like being able to stun, poison, charge their attacks, heal themselves or others or reduce your defenses, or the fact that they’ll frequently switch positions to ensure that the first one is the one most capable of taking the next hit."

Now there's an idea for an RPG: Jebus - the RPG

The game lets you walk on water, cure blindness, duplicate food items, be a healer, and of course die in the end.

actually there has been few video games, based on christian mythology. I doubt its possible to make a game where you play as Jebus himself, since there will be many people to overreact - but probably something close to what you've said already exists

May find something among these.

The first game where item duplication exploits are part of the intended gameplay.

Sadly I don't think we'll get a choice of good vs bad endings.

Might and Magic 1 says hi. (Also, MM2 has one part where the intended solution to a puzzle involves something that a reasonable player would consider an exploit; I encountered something like that in Wizardry Gaiden 3 as well.)

Also, some of the Might and Magic games (2 through at least 5, I believe) have a spell called Walk on Water; 0 guesses as to what that spell does (any more and it would be too easy),

The problem is that the equations are a bit too complex. The nice thing about SaGa 2 is that the formulas are simple, and there are common elements to them (for example, any attack that's affected by the target's DEF (other than ChainSaw, which either works or it doesn't) subtracts DEF * 5 from the damage dealt. Also, the forumlas differ dramatically; there aren't any attacks that depend on a mix of stats for damage, or that are basically the same thing with different constants (rather, you might have different weapons that use the same formula with different constants, as is seen with martial arts, for example); there's no partial defense ignoring (leaving aside one bug that affects spell damage late in the game).

In other words, it's very obvious, in SaGa 2, which attacks work better for different setups. The only criticism is that the information isn't conveyed to the player in-game, but fortunately the (sadly JP-only) remake fixes that.

I could also point out that the formulas are strategically similar to SaGa 1's formulas, the main difference being the removal of the divide by 4 step. This results in combat being much more lethal in SaGa 2 then in SaGa 1; to compensate, death was changed from a condition that can only be cheaply cured a limited number of times (there's more expensive ways around it, and more expensive is easily affordable later on) to one that wears off at the end of battle. On the other hand, I don't like how SaGa 2 gives enemies infinite uses of their attacks when SaGa 1 didn't have the issue.

(By the way, there's also a big plot difference between SaGa 1 and SaGa 2; SaGa 1's plot can get quite disturbing at times, while SaGa 2 is a lot more light hearted.)

Well, if the game is made by an atheist (or other non-Christian), it might give you that choice.