We all know that it wasn't exactly off the shelf but it's design nowadays pretty outdated. It still more closer to pc gpus than you think. The gamecube basically represents alot of pre DX8 PC GPUs. It wasn't using anything exotic like sgi's coprocessor from the N64 or powerVR graphics which didn't support hardware T&L like the ati flipper.
I'm aware Flipper and Hollywood had similarities with DX7 era PC GPUs, point I'm making is Nintendo has never used an off-the-shelf GPU for its home consoles.
If Wii U's GPU was off the shelf we would have known its exact make and model ages ago, we would know every little thing about it. The reason we don't is because it can't be identified as any existing GPU. It's a modified design to meet Nintendo's specific demands regarding power consumption, heat, processing power, etc.
Only on the surface. The TEV Could do things the Geforce 3/4Ti Couldn't do and vice versa and could even pull off some of the same SM1.0/SM1.1 etc' effects with a bit of work, so I wouldn't really say it's similar to Direct X 7 GPU's at all, when programmed it's way, the Flipper could easily pull it's weight.
With that said though, even Direct X 7 cards such as the Radeon 7500 had programmable pixel shaders to a certain degree, just games never used it because it wasn't standard in any major API's that games targeted. (Which is the same Story with Tessellation on the Radeon 8500, 9700 series, at-least a few games used it.)
Ironically, Flipper and Hollywood isn't based on any of AMD or ATI's prior generation of GPU's as it was designed by a company known as ArtX before ATI bought them out, that team then wen't on to build the R300 series of GPU's which pretty much dominated nVidia's Geforce FX, there are some minor similarties in R300 and Flipper on a very very low level though, I still wouldn't even call them cousins thrice removed.
As for the Wii U's GPU, we know it's based on a Radeon 5000/6000 series of GPU's since it includes Tessellation and Geometry Shaders, what extent Nintendo chose to modify that class of chip remains to be seen, but it's certainly a closer relatation to PC GPU's than the Gamecube or Wii ever was.