Uncharted, Valkyria Chronicles, and SF4.
Uncharted simply because because of the story and gameplay, I think 20 years down the road someone can pick it up and still enjoy it as much as someone who played it on day 1. Not counting the graphics are vibrant, and the voice acting is top notch. It has that same timeless feel like an Indiana Jones flick.
Valkyria Chronicles for similar reasons. If you like tactical RPG's then this game pretty much hit the nail on the head of this genre. The story is entertaining and keeps you engaged. On top of that is the art style. I just don't see this game every looking so bad to someone they can't stand to play it. It's not the best graphical achievement of all time, but they chose an excellent art direction. It's cell shaded, but not too kiddy, or trying to be too realistic.
Street Fighter 2&3 are still among the best fighting games of all time, easily, and they've been out for awhile. I see no reason SF4 won't follow that tradition.