Running a virtual machine will need a lot of memory. I don't know anything about those games, but if they have graphics any more modern than Morrowind you'll have trouble with VMs. I don't even know if Parallels' VMs have DirectX support but I know VMWare's only have experimental support.

Darwine runs on PowerPC, but not easily. I'd imaging the reason is something to do with the fact that the instruction translation for x86 is mostly complete, whereas PowerPC's set is still pretty heavily in development. Not to mention that WINE was written for x86.