Don't discount Super Monkey Ball. That game was retardedly fun when I played it, and I didn't even get to the Monkey Pool and shit like that.
Plus, the GameCube price has GOT to fall. Nintendo will have to cut it, probably to $149. I know they're saying they're not going to, but that's what they said back in the PlayStation/Saturn/N64 days too. To compete, it will have to be lower priced. It simply can't compete with PS2 otherwise.
Metroid Prime is really the game I'm looking forward to on GameCube. That and Soul Calibur 2, which is being designed around GameCube's controller.
Halo is seriously an unreal game. Its depth is amazing - the attention to detail will blow you away. Xbox is worth buying just for that. Especially at the $199 price.
If you already have a PS2 and are happy with it, then yeah, Xbox doesn't seem so great. But if you're looking at a next-gen system, Xbox has pretty good games so far and all the cross-platform games are better on Xbox. I'm pretty platform-agnostic when it comes to the big three - PlayStation was my favorite thing in the world, then Dreamcast... right now I prefer the Xbox simply because it plays better (no pop-up, slow down, etc). But I'm not a fanboy zealot type - whatever works best. Which is why I also own a PS2 and will be getting a GameCube whenever the price falls
Real big PS2 advantage - lots of games can be had cheaper than $30. GameCube and Xbox still have some catching up to do in that area. Also, now that PS2's controller and memory card prices have fallen, it's looking more attractive - Microsoft and Nintendo should respond with controller price cuts and cheaper memory cards.
Ah... it's a good time to be a gamer
Now if only I had more time to waste...