Agreed. I think linear puzzle design in adventure games can make them more frustrating and boring. IMO that's part of what made adventures like Monkey Island stand out compared to others: that they gave you access to many areas and had you working on several puzzles at the same time. Stuck in one place? Go somewhere else, try to solve a different puzzle first. Some adventure games though hinder your progress by putting a single obscure puzzle in your linear path and if you can't figure it out right away, there's no point in continuing to play them; you're really stuck then.

Linearity is fine if the game feels open, has big free-roaming levels instead of claustrophobic corridors or streets which are blocked in.

Baldur's Gate is a good example of a linear game, but due to those huge maps (especially the wilderness maps) the game feels open. I guess other examples would be Urban Chaos and Syndicate Wars, linear level-based games but each map is quite large and completely open.

What is unforgivable is linear games that ~feel~ linear, where the illusion of freedom the aforementioned games had doesn't exist and you realize just how artificially small and linear the maps are. Probably the best modern example of this is Shadowrun Returns, for me at least that game fell apart after the Morgue once you realize that it isn't a huge cyberpunk city, it's just a series of small maps where the only way to leave a map is to click to enter a pre-set location to advance the story, you can only click to enter a location where the game says.

Quick time events! :P

I don't know that I entirely agree with your assessment of what critics mean, but I can see where you're coming from. After all, many critics to my knowledge didn't smack the Last of Us or the Uncharted series down for being very linear, both in plot and design (often while the levels may have allowed for some alternate routes, they were largely still constrained to being nothing more than slightly wider corridors).

However, I definitely agree with you in terms of Deus Ex, as it's a wonderfully designed game in terms of very open levels yet a focused narrative coursing throughout it regardless. In fact, Deus Ex is a prime exemplar of something I've written on at some length, regarding the benefits of hub+branch world designs over purely open world, macro-hub designs. As it stands, open world games fall prey to what many have already noted here, the desaturation of substantive content through attempting to permeate a largely uninteresting massive hub with interesting experiences. They try to override this, almost ironically, with a linear narrative, but this is undermined by the contrasting player experience of screwing around doing things opposite the character persona and the absence of persistent repercussions in the larger world.

For probably many people, this is no big deal, but for those that want to feel they've had some effect or made some progress that's lasting, I'd say it definitely is which is why they may be drawn more to linear games. Some of these games burn the world behind you, not allowing you to see that your actions were inconsequential, making it almost impossible to lose motivation to see the game to its end if it's all designed right. If it's designed especially well, the events that torched the world behind you, making it inaccessible, will only motivate you more to continue. (If it remains accessible, NPC dialogue reminding you of events up to your point may also serve to reinforce your continuation forward, rather than backtracking.)

Either way, each design has its place, and I think the greatest failing of open world games is in a mixture of things ranging from structured, exhaustive microcontent (fedex quests/kill x guys/access set point to reveal additional content/area completion/etc.) and macrocontent (core narrative) to the limited surface and subsurface environment designs (overworld map and dungeons). Where linearity is beneficial, and why I don't think it's as taboo as you may think, is that it may compel more nuanced focus on "little" things such as distinct settings, characters, and interactive experiences as well as bigger things like each of these actually having some impact in each of them.

This isn't to say open world games can't have the perks of linearity, only that they often take them for granted and don't apply them in their designs at all or very well.

Well, since we grow up in civilisations that give rather limited motivation/advice for creating your own experience in life, most people need someone to hold their hand and tell them stories and not give them interesting possibilies and freedom, because they do not know what to do with it and think it's just boring.
A life in rails lets you tend to a similar consumer behaviour of course, that's why people go to discos, cinemas and watch sports in TV rather than making music, adventures or training themselves.
Many people still want the illusion of freedom though in life as in games, but they feel lost when having it for real, just look at what people often say about Fallout or Morrowind.

I usually am not bothered by linearity if the story is good. The new Tomb Raider game is linear enough and it didn't bothered me. I rather loathe repetitive stuff, like DAII, where almost every area and every dungeon looked about the same.

I don't disagree, but I think we're kind of talking past each other a little. I'm looking to address the open world veterans that don't feel lost, but know all too well the boundaries of their illusion of freedom, which may lead them back to linear experiences where they don't feel BSed by the world as much because they know the path is charged with something worthwhile or more varied. Open worlds BS you with the illusion of freedom by providing only exhaustive content, with minimal emergent content.

To my knowledge, there are very few games yet that provide really great emergent content, be it through procedural generation or interacting AI.

Tomb Raider is a good example really, the old TR games were completely linear level-based, BUT they never felt linear because the levels were large and their were many secrets. The game had a wonderful exploration feeling and it never felt like the game has telling you where to go or "holding your hand". The fact that the old TR games didn't have music except at specific times (kinda like Half-Life) actually made the huge "alone" feeling of the levels even more pronounced.

Compare that with the modern TR reboot which feels linear, cramped and artificial.

It's a good example of how to do linear and how not to do it.

I always felt lost in the first Tomb Raiders because of the horrible camera and erratic flea-jump-shooting which made the camera problems a lot worse. ;)
But I get what you mean.

Soul Reaver 2 is very linear but you don't have this feeling all the time and a lot of fun and so is Vampire: The Masquerade Bloodlines, but still sometimes I like to roam around and find stuff I'm not really supposed to find at this stage of the game and create alternative timelines and endings.

The perfect example for a not linear game is Notrium (freeware) by the creator of Driftmoon.
Nothing there is linear and the endings don't have much to do with each other, even if you decide to always play the same character.

And yet I loved the TR reboot.. Probably because the gameplay was better as in the old ones. The old ones always felt clumsy for me, and I usually gave up at some point.

One of the reasons why I've never got into the older TR games. I haven't tried the remake of the first TR. But as I said, for me the new TR was pretty nice. I must be getting old... :D

As long as the story is good, it doesn't matter.

I was really enthralled by the Prince of Persia games and not even the story is much to talk about there. So maybe I should reformulate: if the atmosphere/story is right, then why not?

In the case of RPGs, of course I'd like to explore every nook and cranny and to choose the order in which I'm doing the quests/missions, but it doesn't necessarily always have to be open-world for it to be a good RPG. In my opinion.

I agree with everything you have said, that linearity is generally not bad by itself, but I also wanted to add there are some genres and games where even total linearity works if done well and the games are enjoyable. :)

I also agree with what Reever has said:

On the flip side, sometimes a game being "open world" can detract from the rest of the game, when it isn't done well, examples: lack of stuff to do or constant repetitive quests that are all essentially the same quest or those "new" locations are just reused old ones, etc.

In the end, I guess what I am trying to say is that, regardless of linearity, a game is good if done well. If a game works better being linear, why wouldn't it be so?

Or play videogames (linear or sandbox) rather than learning to code themselves? ;)