I basically second everything that was said here, and just want to add:
1. Why the fuck is Braid not here? Yes, I know, everyone knows that one, except you CANNOT EVER assume that people you're talking to know it! Because what if they don't? Then they're going to miss out just because you assumed!
So, if you haven't done so already, BUY IT AND PLAY IT, even if you're not into puzzle games, even if you'd just play around with it for a while and go through 2-3 levels of each world, it's still worth it thanks to the ideas it inspires. (Though I strongly recommend finishing it because the story is amazing too.)
2. If you're interested also in maybe less polished games, but those which try to be different, I recommend Pathologic (first person story, dialogue and metaphor-heavy surreal survival rpg/adventure, well worth the time if you can get over oldish graphics and not exactly great localization from russian). And Void (not "The Void", but the one made by the same guys as Pathologic), which is the closest gaming equivalent to surreal paintings I know (and not just by aesthetics, but by story and game mechanics too)
