Buy Alan Wake if you haven't. I've played through it several times on Xbox 360, it's definitely my favorite game of this generation, that's not a stretch. I'm considering getting it on Steam just to play through it again and enjoy the feeling of getting achievements for it again.
Aaand I did just that. I just got the franchise pack even though I have both games on Xbox 360 already. I have no way to justify my purchase other than it comes with the soundtrack, has better graphics that my PC probably can't handle, and I really, really effing love this game.