An emulator is a piece of software that uses computing power to simulate another device, such as a video game console or a personal computer. As a general guideline, the Wii is capable of emulating most popular home consoles up to around the fifth generation (the N64/PS1 era).
The Wii has hardware that allows for native backwards compatibility with the GameCube, meaning such software can run at full speed as they would on the original hardware. While this is not actually emulation, methods that use this hardware will be included here due to the ubiquity of the term.
Handheld video game consoles
Nintendo DS
Barely possible through DeSmuME Wii. A partial compatibility list can be found here; most games are incompatible or run very slowly.
Game Boy Advance/Game Boy Color/Game Boy
Posssible through mGBA, this is the recommended option. Another option is Visual Boy Advance GX
WonderSwan
Possible through WiiMednafen.
Home video game consoles
3DS/Wii U/Switch
Not possible. These consoles require too much computing power to be emulated by the Wii.
Also note that due to these computing power requirements, ports of 3DS/Wii U/Switch games are also extremely unlikely.
GameCube
GameCube games can be played natively through Nintendont, a tool that lets you play GameCube backups from an SD card or USB drive. All Wiis can play GameCube games, but the Wii Family Edition (RVL-101) & Wii Mini (RVL-201) cannot read GameCube discs, requiring you have a GameCube or an original Wii (RVL-001) to dump GameCube games.
PlayStation 1
Barely possible through WiiStation or WiiSX. compatibility lists for both WiiStation and WiiSX can be found.
Nintendo 64
Possible through Not64, this is the recommended option. Another option is Wii64. Virtual console injects can also be created if you prefer individual channels on the Wii Menu
Super NES
Possible through Snes9x GX. Virtual console injects can also be created if you prefer individual channels on the Wii Menu
NES / Famicom Disk System
Possible through FCE Ultra GX. Virtual console injects can also be created if you prefer individual channels on the Wii Menu
Sega Genesis / CD / 32X / Master System / Game Gear / SG-1000
Possible through Genesis Plus GX. Virtual console injects can also be created if you prefer individual channels on the Wii Menu
Arcade cabinets
You can play most arcade games via the MAME-Wii emulator.
Home computers
DOS / Win9x
Possible through DOSBox Wii. Windows 3.1 and 95 technically work, albeit slowly; this emulator is much more practical for older DOS games.
Commodore 64
Possible through Frodo.
Overview chart
WIP
Emulators that don't exist
These are consoles or devices that will not work on the Wii, usually due to computing power requirements.
- PlayStation 2 and newer
- PlayStation Portable and Vita
- All Xbox consoles
- Dreamcast
- Windows NT (XP/Vista/7/etc)