Hey, games like Star Fox Adventures, Half Life 2, etc. would be "insanely difficult" to do too...about 6 years ago during the age of the PSX, N64, and when TNT2 powered PC's were all the rage.
Hey, just wait till the next systems come out. If first generation cel shading can look as good as it does, I don't see why second generation cel shading couldn't look that great. After all, we are only in the 2nd generation of 3D console games and look at games like Halo 2...