I think Wii U is sorta in a weird spot.
It is more powerful than the PS3/360, but the PS3/360 have 120+ million userbase to the Wii U's 0. So devs are more likely to build their games first for those platforms and then "quickie-port" the game to the Wii U.
It's not sooooo much more powerful from the PS3/360 that it can run the PC versions of some of these games (ie: 1080P+ 1TFLOP or better GPU, etc.) so devs don't use PC assets on the Wii U.







