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.