Yeah, for fighters, it's one the better ones. SSBM is okay, but yeah, not really a fighter.
I'd have to go with Jak 2 if I were presented with your dilemna. I've already got SC2, and while I played through FFX and was waiting for FFX-2 to go down in price I just remember reading a review of it. "Pros: Lots of stuff to do. Cons: Lots of stupid stuff to do."
I've got Prince of Persia: Warrior Within, but it's not really a platformer in the way that the Jak and Daxter series is, more old school "I can jump with a spin now" kind of action. Hmmm, maybe after my current batch of games, I'll go swing by the bargain bin.