The reason being my backlog...
Beautiful Katamari
Big Bumpin'
Bioshock
Call of Duty 4
Crackdown (just achievements)
Gears of War (just insane)
GRAW
GTA IV
Lara Croft Tomb Raider: Legend
Peter Jackson's King Kong
PocketBike Racer
Prey
Rainbow Six Vegas
Rock Band
SEGA Rally: Revo
Sneak King
Splinter Cell Double Agent
Table Tennis
Tony Hawk's Project 8
I plan on just trying to beat each game and not trying to go for specific achievements. I never trade in games unless they weren't mine (for instance I traded in my brother's Eternal Sonata and Viva Pinata because I have no interest in either). So once I beat all my games, then get Soul Calibur IV I can start going for achievements once I start getting bored with SC4.