Download "OpenEmu"
It's an emulator for mac, that can run games from nes, snes, genesis, gameboy/ gb advance, N64, Psone, and a bunch of other older, lesser known systems (multiple Atari consoles, gamegear, and even Virtual Boy, among others)
I use it for N64 games a lot, and probably about 65% of those games run alright on it (Goldeneye does, at least)
But I don't think I've ever had a nes, snes, or gameboy game not work on it. It's got a better layout than any other emulator I've used, as well.