Just putting this out there, but videogames will never have a "Watchmen" in the same way that comics/graphic novels/whateveryouwanttocallitwithoutsoundinglikeyouaretalkingdowntoavalidartisticmedium-s will never have their "Citizen Kane" or in the way that cinema will never have its "Hundred Years of Solitude".
It just doesn't work that way.
When a game comes out that completely ass-fucks the medium - then we will have whatever it is we will have, the only problem is in actually noticing, well....what we have.
Case and point - those in the thread laying the biblical smaketh down on Bioshock and CoD4 while mentioning Deus Ex, System Shock 2 et al. Bioshock is an extraordinary achievement in storytelling that surpasses its near identical spiritual predecessor because of one thing: atmosphere. Rapture feels incredible, yet somehow possible, from the leaks to the audio logs, the attire of the splicers, the relatively benign presence of the Big Daddies and their eerily miniature charges....not to mention the truly incredible audio. Yeah, you can wank about it all you like with wonderful phrases such as "multi-layered meta-narrative", but Bioshock lives and dies in its setting.
Also, CoD4 proved to us that war shooters could be something so much more. It proved to us that having strong, addictive multiplayer did not mean that you had to sacrifice real emotion and tension in a story set, for once, in a reality that the target audience could identify as their own.
That is, of course, before it became the most profitable franchise of anything ever - spawning shovelware like I spawn bad similes.
We miss quite a lot of truly incredible stuff in this medium, which is quite a shame, really...
Take Crysis. Fucking silly story. Average characters. Yet, on a good rig, you can witness one of the greatest pieces of virtual architecture ever made.
Anyway, on topic, the closest we have come to a true 'breakthrough' game has probably been Flower. Flower makes us look at the fledgling medium and say "back the fuck up...where is the story, what am I playing as, why am I doing this?" It drip feeds us not what we need to do, but what we could do...in a chilled out, kinda stoned way, combined with a slow reveal of a pretty solid narrative and one of the most interesting concepts of the 'player character' ever seen in gaming.
Also something, something Braid king of all postmodern meta narratives that relies on everything in the game to tell a story that the main character doesn't want to tell himself - let alone tell a stranger something something too fucking tired too fucking hungry, you get the point though, yes? Nothing has fully broken the medium in the way that Watchmen or Citizen Kane or Ulysses or even The Sopranos have all respectively done, and this is probably because of the nature of games as an interactive medium - everything is at the mercy of the player, how can the developer tell a story that they, really, have no control over without taking away what makes games, games - that interactivity?
N.B - Fucking hell this is an unnecessarily long and slightly retarded post.