Like others have said, it all comes down to the gamer.
I have a PS3, a 360 and a PC.
Whenever possible, I use..
My Xbox 360 for Multiplayer games - I find the multiplayer smoother, More enjoyable + I have more friends that own one.
My PC for Single player games - The graphics, and overall experience of PC is much better.
My PS3 for Single Players (when not available on PC), and for its exclusives - I wayyy prefer the PS3 Exclusives over PC and 360.
So it all depends one what I feel like playing.