Look at games 10 years ago. Many of the games that got 9's and AAA status back then aren't the ones of the 6th gen we're currently talking about now. I think the standards we have of what makes a superb good now are TOTALLY DIFFERENT than what makes a game that we will still think is superb 10 year from now.
Things that matter now (but not so much 10 years from now):
How much the game costs
How long the game is
How realistic or technically proficient the graphics look
Also, I think it's mostly extrinsic. For example, if Gears of War (1) were the only GeoW game in existence, it would go down in history as a classic. But now with 3 more Gears games that borrow the same exact mechanics and do little to innovate, it can't really be a classic.