Wow actually I don't really have a favorite. I have all the major ones! The PS3 is great as it doubles as a blu-ray and upscales my DVDs - SG1 looks great on it - it also has amazing graphics and sound - Dante's inferno is incredible on it.
XBOX 360 has great sound and graphcis, and with games like Fallout 3 and other games that allow online gameplay, it becomes one of my favorites some times.
The Wii on the other hand is great for the family - we've spent lots of time playing bowling and other family oriented games.
Of course - I play most of my games on my PC - Dragon Age is amazing on it - by far the best sound and graphics!!!!!
I discuss it in far more detail: http://hubpages.com/games-hobbies/best-gaming-cons