not as good as the GBA games

It's too short. There aern't enough pokemon. Come on, theres only 52. (including Umbreon, Espeon, Ho-oh and Plusle) And you can't catch wild Pokemon. You can only snag them off random jerks in the game. But the good thing is that you can get Ho-oh in it, and transfer him to your GBA games. Well it's just good that you don't have to obtain that damn Mystic Ticket to get him. But it's too bad that you still can't get any of those super-legendary Pokemon in it, like Celebi, Mew, Deoxys, and Jirachi. Wait, you can get Jirachi from Pokemon Channel.

The gameplay is way too short. It's like more then half as short then any of the Game boy colour and Gameboy Advance games. It's even shorter then yellow version an Game boy colour. So the only use of it once you've completed it is just to trade to the GBA ant to train Pokemon. Otherwise there's absolutely no use of it if you do all that stuff on another game. Too bad it's nothing like Pokemon stadium. Because when I first heard of it, I thought 'Pokemon Colisseum' was just slang for 'Pokemon Stadium 3'. But it turned out that it's nothing like The Pokemon stadium series. It's not even a multiplayer game. The only real life people you can verse on it are Game boy advances by using a GBA to GCN cable. Well most Pokemon games tat are on large consoles that you plug into the TV let you verse one of your friends by using another controller, but not on this one. But it's got something that all the other Pokemon stadiums don't have, Story mode, of course, which is where you catch all your Pokemon. Most of them are really crappy, but some of them are really strong, like Metagross, Tyranitar and the three legendary dogs, Suicune, Entei and Raikou.
Anyway I expect better in the next version, Pokemon XD: Gale of Darkness.