Oh shoot. I didn't even think about Gamecube games. That opens up a few more options. Yeah, Soul Calibur II is awesome. The Gamecube controller isn't the most awesome for fighting games, but I'd recommend seeing if you can get your hands on Capcom vs. SNK 2. Just... don't use the Easy Operation controls. Ew. It's a really good fighting game, though.
Also, there are some surprisingly fun Dragon Ball Z fighting games. If you don't take yourself too seriously, DBZ: Budokai Tenkaichi 3 is a lot of fun. I'll openly admit to enjoying the whole "mimicking Goku throwing a kamehameha" thing. Quick note: I didn't know anything about DBZ prior to playing DBZ:BT2. It has an online play mode, but it's garbage. Don't know if that matters to you or not. DBZ Budokai and DBZ Budokai 2 are Gamecube games that are functionally 2D fighters (3D fighters on a 2D plane). DBZ:BT2 and DBZ:BT3 are Wii games, and they are fully 3D, but you are always locked onto your opponent.
Likewise, there are some good Naruto games, too. The Clash of Ninja series (I believe CoN Revolution 3 is the most recent installment) is really solid. They're not the deepest games in the world, but you still gotta put some effort into winning. They offer up to four combatants in a given fight; free for all and team options are available. The series utilizes 3D gameplay.
For both the Naruto and DBZ games, you don't have to be a fan of the source material to enjoy the games, but you will probably like them more if you're an existing license fan.