RetroArch is a modular multi-system emulator system that is designed to be fast, lightweight, and portable.

List of included libretro cores:

NES: FCEU, Nestopia, QuickNES
SNES: PocketSNES, SNES9x-Next
GBC: Gambatte, TGB Dual
GBA: Meteor, VBA
Genesis / Sega CD: Genesis Plus
Saturn: Yabause (Very slow!)
Playstation: PCSX-ReARMed
Atari 2600: Stella
Chip8/16: Maxe
Arcade: iMAME4all, MAME078, Final Burn Alpha
Mednafen cores: PCE-Fast, WSwan, PSX
Natives: NXEngine (Cave Story), PrBoom (Doom)

RetroArch Android on a Galaxy Note 2
Watch this video on YouTube.

https://play.google.com/store/apps/details?id=org.retroarch