I've always been a playstation guy (Playstation, PS2) but with everything im hearing about the two next-gen consoles my next puchase will be an xbox.
My next purchase will be a Wii. Then in about 12-18 months, I'll get a PS3.
I've played all 3 new consoles quite a bit at various friend's houses. The Wii is just plain awesome, the PS3 will have the exclusive titles I want to play, so the decision is easy for me.
The 360 has some good games. Gears and Dead Rising are alot of fun. However, as a whole, the 360 is very underwhelming. Furthermore, Halo is the single most overrated game series in history.