Let's see here:
Fable III- Because Fable II was freaking awesome!
Halo: Reach- I've been playing Halo since the original on Xbox, so of course I will get this.
Enslaved: Odyssey to the West- I'm going to get this to give to someone as a Christmas present.
Either:
Call of Duty: Black Ops- I've always wanted to try Call of Duty (I've only played a little of CoD 2) and I'm studying Vietnam right now, so there you go.
FIFA 11- I'd just like to see how many goals I can tally in a season with Chelsea, though that multiplayer looks fun.
and finally...
Plants vs. Zombies XBLA- Because Popcap rocks my socks!
Assassin's Creed can wait because it drops in price so fast. I'll probably ask for Fallout for a Christmas gift. Two Worlds II and Gothic 4 will have to wait. I'd like to see reviews of the Sims 3 before I commit to buying it on a console. Also, XBLA games aren't announced too far in advance, so there might be more purchases there if stuff like Comic Jumper or Hydrophobia is released.