Using an emulator is really very easy. Making an emulator, probably not so much, but using one is very easy. At least for SNES games, and NES games, and in my experience N64 games(although some of those require a pretty nice computer.)

Oh and all older handheld emulators are pretty easy. Examples are Game Gear, Game Boy, Game Boy Color, Game boy Advanced.

Sega Genesis and Sega Master System emulators are pretty easy too, and then ones like MAME and neogeo, though I didn't really care for them.