Higan

Higan is an open source multi-system emulator that origianally started out as bsnes, a response to innacurate SNES emulators and shoddy ROM hacks. Currently only the cycle-accurate bsnes emulator is the only thing worth using out of higan.

The name Higan stands for 'Hero of Fire'

Higan emulates:

NES/Famicon

SNES/Super Famicon

GameBoy

GameBoy Color

GameBoy Advance

Nintendo DS

http://byuu.org/higan/

Recommendations

Some recommend using bsnes core in RetroArch to get around some less-user friendly implementations of bsnes