Do not make this your first Pokemon game. Heck not even your second one.
1) The music sucks it is so bad that turned off the sound and listened to some thing else. And to prove a point this is the first time I every done that, and I have been playing video game for 20+ years.
2) The battle animation kind of got on my nerves. For example the move surf could of been shorten to an over head shot, but no it showed the first Pokemon get hit and then the second on get hit.
3) The Orr Colosseum you do not unlock this until you have beaten the game which makes this seems more like a chore, because it is the only way to get certain items in the game. And the area is the toughest in the whole game. I would think it would be easier if you could start some of it earlier in the game.
4) Is probably more of a personal opinion. The game just seems to go on and on and get tedious (of course it might of been the way I played the game).
And finally I would recommend getting Pokemon Colosseum more if you want to get a Pokemon game for the game cube. Even thought it does has some weak points like getting Ho-oh, but in my opinion it does have cooler monsters to get if not less of them.