The first game that looks really cool is Assassin's Creed 2. I've watched some trailers and some gameplay footage, and I think that it looks way better than the first one. The AI (artificial intelligence) is way better. Enemies will actually search places that they think that you're hiding, and there are some really cool moves that you can do against them. 

Another game that looks pretty sweet, although maybe not as good as Assassin's Creed, is Modern Warfare 2. It is essentially the 6th COD game. In it, you fight mainly against Russian terrorists. One thing that looks cool is that you can ride snow mobiles. 

Another game that I've already pre-ordered is Batman: Arkham Asylum. I think that this game is really going to be a winner, because I played the demo, and it has really good combat, but is, at the same time, a really good stealth game. I can't wait to get it. I think that it is going to be really, really fun.

I did not mention Tom Clancy's Splinter Cell Conviction or Halo 3 ODST because they are both exclusively for the 360, which (being loyal to ps3's) I really hate.