Download this file. Its called the wii multi rom boot pack. Its has over 2500+ game on all the old school systems. You will need a Gamecube controller and Gamecube memory card though because the wii recognizes it as Gamecube game.
NWii - Multi-Boot Rom Pack 2500+ Console Games [NTSC] ? Wii.Multi-Boot.Rom.Pack ? isoHunt ? the BitTorrent & P2P search engine