Team Fortress 2. TF Classic was still popular before it was released and if you had played PC FPS's then you had probably heard of it. TF2 took the Classic design, added the new graphical style and is still having content released. Not only will it be remembered, but it will be played for the next 10 years.
I'm also tempted to say Condemned. It has some truly amazing sequences and has the best feel of realism in any game I've played. Other may offer a good emotional storyline, but Condemned offers the cold, bleak environment which is designed so perfectly it seems almost real.
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Bioshock won't be remembered. System Shock 2 will be. Deus Ex will be. But Bioshock won't. It's a good game, but probably not something people are going to pick up in 10 years and enjoy as much as they did on their first playthrough.
GTA4 shouldn't be, either. People know the name of the series, but how many of them will actually talk about how it's the greatest game ever (as many seem to claim, although I don't see the appeal) in years to come? Repetitive gameplay, a dull city, it just isn't memorable.
Twilight Princess is only going to be remembered because of the Zelda title. I played it a few months ago and didn't enjoy it. The graphics already seem dated. The style which Ocarina Of Time and Wind Waker used were better, as they didn't have the effects which are constantly changing like TP does. One of the worst Zelda games in my opinion.
Call Of Duty 4 will be remembered for having a horrible online community. The single player was amazing first time, but the multiplayer offers nothing more than Call Of Duty 2 other than graphics, which is why many play it.
The Mario games (Galaxy and New) are going to be "just another Mario game" because that's what they are. While people may think that Galaxy did something new and exciting you have to ask: did it? My answer is no. It isn't as good as the classic ones, or even the Paper Mario RPG. The worlds were small and some were clumsily designed. The gameplay becomes repetitive (not as quickly as GTA4, however).
Metal Gear Solid 4 is the worst in the series in my opinion. I've only played 1, Twin Snakes, 2, 3 and 4 but I don't like the way 4 became so action-heavy rather than the classic stealth. Then again, my favourite is my first: Metal Gear Solid 2, which lots of people seem to dislike.
I like most of those games (the only one I dislike is GTA4, but I wouldn't play Galaxy or Twilight Princess when I could play any other Zelda game or Psychonauts) but they just don't seem like greats.
If Shadow Of The Colossus was remade with high-definition graphics that would go down in history. I can only dream.
