Which game to buy?

Well, so my parents told me I could just get a game for Christmas. Since they are gaming noobs they dont know whats a good game so they let me get the game.

Now, which games really are worth getting? Im a Xbox 360 player, and I really like co-op games and solid multiplayer games (like Halo, a multiplayer that isnt abonded within a few weeks) Honestly I cant think of that many games. The only ones that come to my mind are:

-Modern Warfare 2
-Forza Motorsport 3
-Left 4 Dead 2
-Assasins Creed 2

Like always I really only look at those series games which have a good reputation. But which games are worth getting for Christmas besides these? You really dont have to tell me ''go for MW2'', I just want to hear which games are really good.

with what i hear l4d2 is probably best choice. IMO i wouldnt buy any on this list.

I'd say L4D 2 would be awesome! just because killing zombies never get old lol

but MW2 if you wanna unlease some nukes lol

Topic can be closed, I decided to go for MW2 as it has a good co-op aswell plus the multiplayer will last longer then L4D2's multiplayer.