Goldeneye on N64 took 3yrs to make and is regarded by many to be the best game in the world and it fits on a 16MB cartridge. The N64 only has a 4MB display memory size so I'm sure if a game was developed full time for a few years on Amiga hardware it would be fairly mind blowing.
A Blizzard PPC with BlizzardVision would have a third to half the power of a Dreamcast - a huge potential there had these cards sold better.
Pity we never really got 3D development software like DirectX for the PPC accelerators... then again, with retro so popular someone could make a killing by selling plug-n-play 3D hardware for old Amigas (so long as there was a killer app or conversion to accompany them!).