A great thing about homebrew from the Wii is that it allows you to play video games from a wide variety of older generation systems by using emulators.
The Wii has various emulators available that let you play NES, SNES, GB(A), Nintendo 64, ... games with ease! The setup for each type of emulator is a little different, but of course this guide will help you!
Full list of emulators: http://wiibrew.org/wiki/List_of_homebrew_emulators
► GX Emulators -- A group of emulators that look the same and act the same. The only difference is the system they are made for.
► Wii64 -- An emulator for Nintendo 64.