I've got gamecube, and it pretty much rocks. As a 21 year old college guy, I must say I was weary of the system at first. But playing games like
Super Smash Bros. Melee
Monkey Ball 2
Mario Sunshine
are fun as hell. Especially the 4-player ones. We've already put in about 120 hours on Smash Bros. in the past 2 months, its so damn addictive. Especially on a 42" HDTV
Plus, there's loads of great 1-player games out or nearly out... Eternal Darkness, Metroid, Resident Evil, Starfox Adventures, etc.