x86/dos (very very old PC games)
Amstrad 6128
Amstrad CPC
Apple II
Atari 800
Atari 2600
Atari ST
Chip- 8
Colecovision
Commodore64
Dragon 32/64
Dreamcast VMU
Gameking
Gameboy/Gameboy Colour
GameGear/Sega Master System
GBA
Megadrive
Macintosh
MAME
Msx
Neo Geo AES/MVS
NeoGeo Pocket
Nes
Oric
ScummVM
Snes
Spectrum (ZX Spectrum)
Thomson MO5
TI 83 Calculator
TI 85 Calculator
Vectrex
Watari Supervision
Wonderswan
ZX81
Individual Arcade games emulated:-
1942
1943
Aemio
Bombjack
Ghosts' N Run
Green Beret
Klax
Marca
Mr Do
Pong
SnowBros
Solomons Key
Space Invadors.
There is still yet more for DS flash kits in the way of homebrew and ports
homebrew is unofficial software for the DS
ports are usually PC games originally that have had source code released and that code has been used to make that game work on the console, the most famous ported game is Doom, for ports you do require the original game data files, though most do come with demo data files anyway to get you started playing