I find it more appealing to play games on than any of the other consoles. The controller is more comfortable than the PS2s and certainly more comfortable than the XBoxs. It's more powerful than the PS2 in almost every way and it has a much better selection of games than the XBox does.
Plus, I happen to think that Nintendo makes the best games around. The Gamecube has been about changing the way each of their big series' is played, and so far, (in my opinion) almost every big game they have released has been the best in it's respective series. I vastly preferred Mario Sunshine to Mario 64, Wind Waker just felt more like a Zelda game than Ocarina of Time did, and Metroid Prime is the perfect realization of the Metroid series in 3D.
I love my PS2, but I prefer to spend my money on Gamecube games. And I just flat-out don't like the XBox.