When my son Dave got Super Smash Bros. for the WiiU, we also got him the Game Cube controller adaptor for the supposed best play experience. Already had some GC controllers because he had been playing some GC titles on the Wii (mainly Sonic related).
Yea now I just need a game cube to play it on. My biggest selloff regret is selling my game cube. So so dumb. Such a great system!