Really hard, but fun at the same time.
I actually found a way to get to Neo Geegus without having to fight all opponents. I don't know if anyone knows about it, or if it's just a glitch only I have, but if you fight the opponent you got in Arcade Mode in Vs. Mode, you advance to the next round in Arcade Mode once you beat him in Vs. Mode. Pretty cheap, huh? xD