2. Atmosphere
There are a few games that do the whole post-apocalyptic wasteland thing. Borderlands might look pretty similar on the face of it, but the world is populated with a compelling list of characters and a great sense of humour. Unlike many games with this kind of environment, it doesn't take itself too seriously. In fact - thinking back to the absurd crash zooms and parenthesis information on character introductions - it doesn't take itself seriously at all, and that can be pretty refreshing.