I have a Gamecube and up untill recently that was all I had, then I bought myself an xbox just after Xmas, and I really havent found myself buying that many games for it, I mean sure there was some must gets like KOTOR but since that I really havent "needed" to get another game..
Gamecube is solid though, FPS Always great, loading times (better then xbox or ps2 thats for sure) Spec wise its the 2nd most powerful out of the 3..and tbh you cant really see a difference between that and ps2..but it is
With games like Metroid Prime, Metroid Prime 2 (coming out with some killer multiplayer), Res Evil 0 - 4, Soul Calibur 2 (yes I know its multi format but the Gamecube version has the best exclusive character), Zelda Wind Waker (sure it might be for kids the cel shaded one, but if you get the bonus disc its worth playing OOT again)....the list goes on some good, some bad, ppl hate games, some like and so on.
I would advise getting the cube if you want some solid fun...if you want serious games Id go for maybe the xbox but then its the most expensive...games are about the same price for any console.
PS2 Ive never had, but ive played it and it is good, however the shape im not a big fan of...games are in good supply with games like Final Fantasy (which is on gamecube as well now so...) and Metal Gear Solid (also on GC now but as a Remake).
With a general rundown on consoles id say this
PS2 Would be great mix between GC and Xbox, however its clunky with FPS issues and loading times arent the best.
GC Is probably the best loading and has some of the best games around (yea not all the games are great but they have decent ones) and its fun for all.
Xbox would probably be for the serious gamer, however Its worth alot and I would rather get something cheaper for less money with more games.