Because, something realistic and mature, would very likely require a emotional and time investment for a return of something that could be provoking, disturbing, possibly even painful, depressing, or infuriating. In short, it wouldn't be fun. Like watching Schindler's List. That is a extreme, but it illustrates my point. Something like that would be very hard to sell to the current Demographic of gamers. Hard to sell in general, as a key difference between movies and game, is interaction. The most trying film still only requires the viewer to sit, watch and listen. A game requires you listen, watch, and interact. It's asking a lot of someone to sit, watch, and actually play through themselves of something that isn't going to be fun, even if it is entirely thought provoking.

 I'll give you an example. Let's say I'm going to try and make a game that's realistic, and deal with mature themes. The game's purpose will be to help the player understand the incredible pain and grief, of a convicted prisoner who is actually innocent. 

In my game, you play a character who starts with an average life and average job. You, playing as this character must perform mundane tasks of their work. If you mess up, it causes annoyance and spurs more mundane and uninteresting work to rectify your mistakes. This continues until a day you are arrested for a crime you did not commit. (A detail you're made completely aware of) At this point in the game your character is stuck between going to jail and court. Over, over, over and over again, in a slow trial of which you have almost no influence over. The player will have to continually sit through the trial, and desperately work with his appointed lawyer in attempt to prove his innocence. A section of the game I would in vision would be spread out over several hours. This would prove ultimately feudal and your character is convicted and sent to prison.

In prison, you’re subjected to many things. Vicious assaults you are unable to adequately defend yourself from, little understanding of where you are, the threat of rape. Ultimately most of the time your subjected to routine, work, and monotony. As a prisoner you have no freedom, and must go and act as told or suffer the consequences. In the game fatigue from being injured, tired, and such will cause the controls to suffer as well. If your character becomes fatigue, you will have trouble controlling him/her, and this will lead to possible failings and mistakes in your duties, that lead to further fatigue. This cycle of tiring repetition and painful punishment you have little defense against will continue for many many hours.

Your character eventually has the opportunity to attempt to purchase and use drugs, however there are very difficult to acquire, and require much time and even more effort than needed to simply continue. Use of drugs create for an extremely short section of possible pleasure. Portrayed by subtle changes in art style, and a temporary removal of game play elements intended to cause pain. These highs would be very short to the relative length of the game, but are designed to be pleasurable and provide relief. They will end extremely quickly, and you will have to attempt again to get more. These highs will eventually last less and be more dulled, but still provide a sharp contrast to game’s intentional repetitive suffering.

This all would continue for twenty cumulative hours of game play until suddenly your character is informed that new evidence as since proved his innocence. Your character is required to leave the prison, now a free man, and the game ends after stepping outside the prison walls.

This game is intended to allow players to suffer the horror of losing your life to a routine of abuse, pain, and largely monotony, despite entirely knowing that your indeed not suppose to suffer this punishment. You’re never given an opportunity to commit a crime outside before your imprisonment, and much of the game would be designed to instill boredom, coupled with anger, frustration to convey this message.

Okay, first of all that is just an example. I’m not making statements with it, just giving a possible scenario of someone earnestly trying to make a mature realistic game intended to emulate a disturbing situation that does happen. Can you imagine how hard a sale this would be, to anyone? To try and convince a publisher to front money for this, or a gamer to buy it, or even try it for free? The game is specifically trying to recreate a terribly unpleasant situation, and unlike a movie, you must also participate to gain the benefit of this experience. It’s a lot to ask of someone.

This is an extreme example, but I did it to highlight all the reasons why we don’t see many games with realistic settings and addressing specific issues. Like Bod said, they’re often Fantasy or Sci-Fi, not just because geeks like them, but it also immediately detaches it from reality. Even WWII shooters intentionally ignore the horrors of the actual War entirely to favor the gloried action-move-esque aspects. A WWII shooter where you visit a concentration camp would likely upset the player, and remind them of horrendous loss of actual human life, and could possibly discourage from continuing to play.

Even when games do attempt to address more difficult topics, it’s still often done abstractly, or deliberately distanced from reality to an extent to avoid of things becoming too real, and game play of course will be fun to keep the player happy and playing.

Games are still entertainment. A game may have an upsetting story, but unless it's also fun it will likely go 
unsold. And this in itself is a conflict since you may wish to express something painful but must make accomdations to include a signifcant protion of it to be fun as well so that the market will support it. If the gaming market expands to enough people, and becomes affordable enough to enter we may eventually see games designed to be something other than fun, at which point we'll stop calling them video games. But I feel that's a long way off.

It is impossible for me to play any of the following games without thinking of them as art:

Xenogears
Silent Hill 2
Okami
Viewtiful Joe
Xenosaga I,II,III
Persona II
FFVII
FFIV
FFIX
Grim Fandango
flOw
Ico
Shadow of the Colossus
Super Mario 64
Legend of Zelda: Ocarina of Time
among plenty of others that deserve mentioning

EDIT: Completely forgot about the Metal Gear Solid series, arguably one of the highest on the list. 

I honestly think that video games have as much potential or more than some other art mediums because of their interactive nature. It is like reading a story that you play a part in (and please, don't compare to choose your own adventure). That sense of volition that Ebert Roper looks at as restrictive is pretty liberating.

Sure I like games that I can just play and relax, but I personally look for more than that in a game. I look for something that channels an intellectual experience through the game.

See.  I just see it as Irrational games loving to give you multiple ways to blow stuff up.  Look at Freedom Force.  They're all about options.

Also while Eternal Darkness was possibly my favorite Gamecube game. I never got a insanity effect unless I wanted to. Your bar just had to drop way to low.

The word game is list at m-w.com as a activity that is a diversion. Video game's definition over there is a little out dated, but niether mentions fun.

Akuma's list is great for some games as art. It's funny that you didn't mention FFVIII, it's nowhere near my favorite in the series but it tried to do something that no other FF game has (that I can think of). Levels are mostly irrelevant in FFVIII, while this kills the fun of going back and slaughtering earlier opponents, it takes the grind out of role playing and can make the game more immersive if you ignore stats and stuff like that. Oblivion does this too.

Metal Gear Solid 1 to me is one of the most immersive and dramatic games that Akuma mentions, the story is there but the real experience is the gameplay. The sequels got more and more melodramatic, but the first one is a good example of gameplay affecting the players emotions more than the story, with out relying completely on killing-shoot-em-up action.

Like I said earlier, SMB is like a piece of art from a master of gameplay and surrealism. God I am such a Shiggy groupie, but you know what he deserves it. SMB1&3 and SM64 all fall into this, galaxy is coming along nicely.

Elebits would have been perfect with out the cutscenes. If they had only done the narrative a little differently I think that game would have been recieved and reviewed much better than it was. The gameplay is like what you would expect a family movie should play out like. Twisting, turning, lifting, searching. If you could get over the flaw of the bad narrative, this game would have you making faces that you hadn't made playing a new video game in a long time.

Mature isn't really the right word, because it is used too many different ways when relating to games. Let me use it in a sentence a little differently, maybe that will make my purpose a little more clear:

Gaming as an artform is maturing very slowly. This maturity is key for a mainstream audience to become part of deeper gameplay experiences. Maybe Nintendo's casual friendly approach will help it, maybe it will be MS's media-center features and rich online experience, maybe it will be Sony's larger format and social network (Home), or maybe it will still progress slowly. I think in the next couple years we will begin to start seeing the true next level of the artform.

100% true. Although I myself still love and cherish Nintendo's games. The Zelda games were never story driven but god damn they game the better gameplay than most story driven games! Metroid Prime might not be THAT heavy on the story but the little it offered was more than enough to make you part of Tallon IV/Aether!

I love story driven games by far [favourite games ever are the Golden Sun series right along side the first Metroid Prime]. I'm just wondering if you're willing to miss out on classics just because they're not heavily story driven!

I don't agree with that, I think we've had one member here said he speeds through to the gameplay to get to the story in MGS games, and another who skips the cutscenes to get back to the game. This echoes my complaint about gameplay and cinematic aspects being disjoiinted in games. And that for them to grow as an artstyle they need to feel like the same experience. The gameplay in Metal Gear Solid never effected my emotions, even with it's fourth wall elements. Anything emotional was in the cutscenes or the codec transmissions. Sneaking past patrols and shooting them from the shadows was just fun.

If you were to rework MGS as a Comic (I think they already did) it'd probably still have the same emotional impact as the game. The loss of interactivity I don't think would change that, it just wouldn't be as fun anymore. They are called games for a reason, and until more developers try to use the controller has the constant means to inspire you, or challenge you intellectually, or the shock you, I feel it will remain that way. People like Ebert will look at games with "good" stories and likely believe they're just being butchered and shoehorned to fit in the confines of a traditional game, and not give them a second thought.

I have no idea what you are trying to get at here because you seem to put a stereotype on gamers. I personally think that you are wrong and all three companies try to push storytelling in their own way. Heavenly sword, MGS, metroid, bioshock, halo, lair. All these games seem to have many elements and you seem to accost them for what you can percieve.

Take for instance Halo, you may see it as silly hardcore gamers concerned about this green armored dude saving the earth. I honestly am looking forward to seeing if Cortana has gone rampant or not. If you do not understand what I mean then you must admit to missing something.

Lair seems to have a story that trys to play out a morality tale between religion, duty and ethics. Bioshock seems to play out a morality tale as well but more about concepts and human nature. MGS stories ( albeit mostly over the top) tells a very complex story about (surprise) morality and ethics. MGS3 and portable ops should have you rooting for big boss and has the gamer take another look at liquid and solid snake.

Metroid and heavenly sword do not seem to try to provoke deep thought from gamers but more to provide a cinematic experience. Metroid does it in a way that you can choose your level of immersion yet if you try to run and gun the majority of the story will be laid at your feet. HS try's to push the envelope on cinematics and ninja theory is very clear on their intent as they continuosly show behind the scenes that amaze me.

Video games can be taken seriously but it really depends on the frame of mind that the player has. You may think a game has failed in providing a serious story because they offer unrealistic advantages for the sake of fun. But a serious story is not going to keep you playing a game that is amazingly hard. Most games if they decided to be realistic would be tough. Imagine FPS's without maps, HUD, ammo count and one life if you die there is no continue. Or a game like acecombat with a realistic amount of missiles and damage. It wont work.

EDIT: And on MGS and skipping cutscenes, this is one example of why it is up to the player how they address the story. Without a question those who have skipped cutscenes vs thoughs who got caught up in them most likely have s different point of view on the story and the overall message of each game. Chances are those who skip the cutscenes might like the game less as well. I recently spoke to someone who claimed that MGS was anti war. I said I didn't see it that way and that led to an interesting conversation that shows exactly what typ of information is taken away from the game. there are things in the cutscenes that cannot be done in game because in game you have the ability to divert your atttention.