[Angrist]

I'm always amazed by a huge, living world. Where the world changes even without you. Believable characters that you care about. And a place where you have endless things to do.

Oh and another very important thing for me is atmosphere. Some games have it, most don't. Some that do: Metroid Prime, Zelda: A Link to the Past, Warcraft III, Donkey Kong Country.
Now I realize that all these games have very nice weather effects, mostly rain. And nature. Lush nature is very important for me.