The Raziel levels get much better. Admittedly, they're not as fun as the Kain levels for about the first half of the game.
Either way, though, a Gamecube is definitely worth every penny. Especially for the selection of games you listed there. I actually really need to pick up SC2 pretty soon. I was never tremendously jazzed about it until I sat at a friend's house last weekend playing through Weapons Master mode as Link for about 5 hours. And yeah, Heihachi does suck. The PS2 crowd should have gotten either Solid Snake or Dante. Personally, I think Dante would have been the better choice.