I game on a 360, a wii and a pc, but the only thing I really use regularly for gaming is my 360.
Personally, I don't think I'd ever buy a PS3. There just aren't enough exclusive titles to justify getting one. The only reason I even own a wii is because of its exclusives. If it weren't for brawl, meteroid, LoZ, Fire Emblem, etc, I wouldn't have one in the first place. The only games I could see myself getting for PS3 are MGS4 and warhawk, which is not enough for me to ever buy a PS3. Also, I would cost me more for a PS3 and a copy of warhawk and MGS4 than It would to go replace my wii and its library.
So that's why I would never buy a PS3.
EDIT: Here's something that's kinda old but is still pretty funny about PS3 excusives: http://www.gametrailers.com/player/27842.html