Here's a list of systems I have set up on my PS3 with RetroArch:
Atari - 2600
Atari - 7800
Atari - Jaguar
Atari - Lynx
Bandai - WonderSwan
Bandai - WonderSwan Color
Doom
GCE - Vectrex
Handheld Electronic Game
MAME 2003
Mattel - Intellivision
NEC - PC Engine
NEC - SuperGrafx
NEC - TurboGrafx 16
Nintendo - Family Computer Disk System
Nintendo - Game Boy
Nintendo - Game Boy Advance
Nintendo - Game Boy Color
Nintendo - Nintendo Entertainment System
Nintendo - Pokemon Mini
Nintendo - Super Nintendo Entertainment System
Nintendo - Virtual Boy
Philips - Videopac+
Sega - Game Gear
Sega - Master System - Mark III
Sega - Mega CD - Sega CD
Sega - Mega Drive - Genesis
Sega - SG-1000
SNK - Neo Geo Pocket
SNK - Neo Geo Pocket Color
Everything I've tried works well. There might be some MAME games that don't run as well as others but I haven't encountered any problematic ones yet. In addition, basically all PS1 games run perfectly and any PS2 game that was released as a "Playstation 2 Classic" will work even on a Slim console. If you have a backwards-compatible Phat model then basically all PS2 games will work.
I have no idea what's available outside of RetroArch, but what else would you realistically even need?