I have one of the high-end i7 rMBPs with an Nvidia 750M chip inside. In Boot Camp, I get 60fps the vast majority of the time playing Super Mario Galaxy 2 and Metroid Prime Trilogy with mostly default settings — albeit at 1.0-1.5x internal resolution. Can't complain! Love having all the best Wii games on the go, original jaggies and everything.

In native OSX, performance is 1.5-2.0x worse.

Yeah, this is mainly because Apple's OpenGL drivers are terrible. They're eternally behind the GPU vendor drivers in OpenGL version/feature availability and have worse performance. I'm crossing my fingers that in a few years the clean slate of glNext will give Apple a chance to fix this, but not counting on it...

Hilariously, most of my multiplatform games run better through Parallels (pointing to my BootCamp drive) than in OSX native. How that works I have no idea. (Dolphin is demanding enough to require BootCamp for 60fps, though.)

Interesting. Is the Dolphin inside Parallels using the DirectX or OpenGL driver?

Er, disregard the above I guess; I misread your post as saying Dolphin worked better in Parallels. Or you edited it.