The purpose of the PS3 and 360 are for graphics, yes, but what about the Wii? It was designed to be a next step in the evolution of gaming, not to be as grapichally realistic as possible.
Why is it that every game must have some sort of violence in it? Yes, I will admit i do enjoy blowing up and shooting every living thing around me in GTA: San Andreas in my spare time, but this is not what makes games enjoyable. Most of the N64 games didnt have much violence in them at all, and they didnt exactly look realistic (compared to todays games), yet they were still some of the most memorable games i have every played.
And about the Wii having no good games? How about Metroid Prime 3, Zelda: Twilight Princess, and of course Super Mario Galaxy.