I've NO EXPERIENCE with MAC platform at all so please if anyone is more informed chime in
Still I thought this would be a good place to start. For info, suggests, advice about using a MAC to emulate various computing and gaming platforms.
Apparently from a quick search OpenEmu appears to be pretty nice :
Supported Systems System Emulator Cores Game Boy Advance Visual Boy Advance Game Boy Color Gambatte NeoGeo Pocket Color NeoPop Nintendo (NES)/Famicom FCEU, Nestopia Nintendo DS DeSmuME Sega 32X Picodrive Sega Game Gear CrabEmu, TwoMbit Sega Genesis/Mega Drive Genesis Plus GX Sega Master System CrabEmu, TwoMbit Super Nintendo (SNES) SNES9x, Higan TurboGrafx-16/PC Engine Mednafen Virtual Boy Mednafen OpenEmu is about to change the world of video game emulation. One console at a time...
For the first time, the 'It just works' philosophy now extends to open source video game emulation on the Mac. With OpenEmu, it is extremely easy to add, browse, organize and with a compatible gamepad, play those favorite games (ROMs) you already own.