If you don't have the money, or if you don't have the extremely high-definition (1080p), then don't bother thinking of the PS3. The truth of it is, all the next gen consoles have about the same graphical appearance. The exception lies in the resolution, however, this is where Sony falls. If you do not have a 1080p high-definition TV, then the 1080p that the PS3 outputs will have to be degraded into either 720(p/i) or 480(p/i) or even lesser. Since you won't be seeing what the PS3 is sending - you'll see what the TV interprets and recompiles the PS3's output to be - you might see slightly worse appearance from the PS3 than the XBox 360. Though truth to tell, the Wii games can look just as good or even better than some games on the XBox 360. Oh... but Gears of War is freakin sweet - Unreal Engine 3 owns.
Anyway, the point is, with Wii's overall innovation, it can still keep with the graphical appearance of some (if not most) XBox 360 games and still be incredibly more fulfilling (because of the intuitive Wii-mote). The XBox 360 can, in some instances, look better than the PS3 - otherwise, it looks just as good. The PS3 has better hardware than the Wii or the XBox 360, however, unless you have the 1080p high-definition TV, you cannot really utilize the full power of the PS3.
This is just a short summary of something I'll be posting in my forum sometime soon