In my home there is currently a Wii, a PS2, PS3, Xbox, and a Nintendo 64. My favorite is the PS3, though I do love the Xbox and N64 a lot too.....
On the PS3 I play Rockband, Madden, and Star Wars Battlefront mostly, it really depends. The Xbox was actually purchased just for Halo 2, hence we have no other games for it, but I love Halo. And the N64 just rocks.
I personally feel that the PC dominates, but out of the three next gen consoles, I'd have to say the PS3 is the best. I own all three, but what really counts for me is the free online multiplayer and the insane graphics that the PS3 has. It's almost like a combination of all that is good between the Wii and 360.
I have personally played each system, graphics by far go to the PS3, playability to the 360, and of course the Wii is a brilliant idea due to the fact of the motion sensors.
I have the XBOX360, PS3, and PS2. The first two are the only ones hooked up currently. I prefer the 360 for most of my gaming mainly because of all the features of XBOX Live. I play platform exclusive games on the PS3. I also like being able to play blue rays. In my opinion I think the graphics are comparable between the two, when speaking about games. This is just my opinion.