Actaully, none. In a recent study, the ps3 and 360 have the same graphics. The test concluded that the wii sucks, and the pc owns all. But really if you look at 2 screens, one 360 and one ps3, theres rellt no difference
The Wii should stay far away from questions concerning graphics. Although I haven't played PS3 much, I still would have to say that the 360 has the best graphics so far, I'm not thinking about hardware though, more like Xbox 360 has had more time in the world and developers have more time to play with the graphics the 360 is capable of, while the PS3 having only slightly better graphics, would be hard because sometimes it's hard to choose which one is "slightly better".
The PS3 does have the best graphics its just a slight difference that most people don't notice at first glance. The wii is just worthless in this department..........actually its worthless in every department