The XBox 360 has the most inviting design, the Revolution is the most simplistic, and the PS3 is the most futuristic. Depending on what mood I'm in, I think that would change my answer. Although I definitely do not like the PS3 controller - doesn't look very functional at all; looks more like a renegade artist killed his engineer partner and built the damn thing himself.

edit: The PS3 looks very bulky compared to the XBox 360, which looks bulky compared to the Revolution. Points off respectively for each system for that.