GameCube

Multiple reasons, one being innovative and different games. Case in point would be Super Smash Bros. Awesome 4 player "fighting" game, that is not anywhere close to Tekken in how they play. The controls are very easy to learn, but still annow for enough specific control for some interestign moves. And, it is pretty kid safe, while being fun for adults too. It gets more play time on my system then Soul Calibur 2 does.

And no, the GameCube isn't kid oreinted. Nintendo just manages to release some games fun for all ages. But there are Rated M games that are also a blast. Eternal Darkness is a must have. Better then any Resident Evil game, for the way it also screws with you while you play the game.

The XBox has quite a few games I can also get for my PC, or that have very similar titles on the other consoles. I will pick keyboard and mouse any day over the XBox controller for games like Halo. I do own one for one game though, that being Steel Battalion.

PS2. It has a good selection of games, but I just haven't justified the cost yet. Quantity to me just means way to many games I will want to buy and play, and my GameCube already has several games I still need to beat.