Xbox360 for any Xbox exclusives that catch my eye and for any multi-platform games. The Achievements make for a good motivator for multi-platform titles, but also, the Xbox360 controller is the most comfortable of this generation.
I have a Wii just, basically, for Nintendo games and any good exclusive titles.
I don't have a PS3, but when I do get one--it'll largely just be for the exclusives therein.
I got a PSP and a DS to have them, and for their unique titles.







