A direct response to the NES, the Master System had superior hardware.
Fusion formally known as Kega Fusion is a Sega SG1000, SC3000, Master System, Game Gear and SegaCD emulator. In our opinion Fusion is the best Master System and Genesis emulator available.
Gens Plus! is a Sega Master System, Genesis, 32X, SegaCD and Game Gear emulator that is based on the Gens emulator with additional features. It ranks a close second to Fusion and isn't a bad choice.