I am an INSANE RPG FAN, and if I were you I would go with the PS2.
Let me break out the pros and cons of each systems....
Gamecube - small and affordable, yet still comes with free gamboy player/ no con in comparison of price
PS2 - comes with a built in DVD player/ bigger in comparison and more expensive
Gamecube - a different tone of games, innovative games, loads of great first and second party games and more on the way/ barely any third party support, except from Capcom with RE and the capcom 5 or 4 or something, no sports and barely any racing games
PS2 - great third party games, great RPGs, especially RPGs, great racing games, sports games, all around a good system/ not that much different in comparison to an Xbox
Gamecube - has basically no online future but LAN is on the prow, and starts with mariokart, a guranteed(sp?) hit/ won't start until late this year or early next year (correct me if i'm wrong)
PS2 - has an online and LAN future, already has some great games out/ nothing as good as Halo though
Gamecube - GBA to GC connection/ insane hardware requirements when it comes to playing future games, so have alot of friends
PS2 - you can use a keyboard and mouse/ controllers are more convinient
Gamecube - more comfertable controller, as well as a wireless First Party controller/ wireless has no rumble, and controller doesn't work as well in FPS or fighting games in comparison to other consoles
Ps2 - great controller, can be used well with any genre/ not as comfertable as Nintendos controller (opinion)
I could of put more but I decided to end it there....decide which one you like better and go buy it. Your first mistake was trying to get an honest (non-fanboyish) reply on a GAMECUBE FORUM. I'm sure you've played both, but go play them again on a kiosk anyways or at your friends house just to make sure.