GTA IV
Saints Row 2
Mercenaries 2
Alan Wake
Those are the highest on my wants list, games very likely to be Day One purchases (GTA IV already is since I preordered it from Liongames a while back) Other games that I'll probably pick up at some point (maybe by 2009 when the price has dropped) include Burnout: Paradise, Fable 2, Too Human, and DMC4.
I've still got plenty of games from this year to get to, like Orange Box and Mass Effect (just started ME, only about an hour in) and even older titles like Gears and Dead Rising. No shortage of great games for me to play, now if I could just make the time to get to them all.