technically the wii cant compete, it would be crazy to say otherwise, but good brushes , canvas and paints dont make you an artist.
Its just as easy to create ugly graphics on the PS3 as it is the Wii.
In terms art atistic merit, and overall appealing styles, things such as Elebits, Galaxy, Zack & Wiki are unmatched (atleast for now), but this is down to japanese artistry, the xbox is too obsessed by dark, gritty killing games, which no matter how good they look just dont appeal to me.
You could reverse that and say the exact opposite, but thats just a difference in opinions and taste.
When i look at a game like Galaxy i find it difficult to see how improvements could be made, sure the resolution could be higher and the textures may benifit from more detail but what would be the benifit other than eyecandy? Its one thing to have incredible power, but its another to utilise it properly and i think thats where Nintendo and alot of Japanese developers have the advantage. Galaxy still oozes style and beauty and most of all, it looks like a FUN game, not just yet another man shooting other men/aliens. People of all ages and gender will look at Galaxy and want to play it, games such as GTA, GoW, Halo etc just dont do that.
Basically i think if the developer has the artistic flair, the format is irrelevent, an appealing game is no more appealing to me if its in 480p or 720p.