These days, most emulators use pre-configured mappings to allow any controller that uses xinput to be immediately mapped to whatever the original console used. But that is only possible because of the standardized button layout that has proliferated throughout consoles. Mapping older controllers, such as the SNES controller, to a modern controller is pretty much trivial. Even a PS2 controller can be mapped to an Xbox 360 controller without losing much.
For Dolphin, things get a bit more complicated. While the GameCube Controller has a few trouble spots, …