The PS2 is selling the greatest amount of units virtually everywhere in the world. And it is honestly outdated, and too expensive for what it is. I have a PS2 and only ever play one game on it which is Pro Evolution Soccer.
KDS - Have you ever looked at statistics of game console ownership in the market? The average age of a GameCube owner in Europe is 23. The modal age of a PS2 owner is 14. How many 14-15 years olds do you see going around saying Nintendo is for kids, and Playstation is not - f*cking hundreds of 'em. Perfect Dark on the N64 was rated 18. Eternal Darkness is the scariest game ever made and will sh*t you up no end.
At the moment the Xbox hasnt got enough good points about it to spend £200 + extra for games. As you say yourself you already own a PS2 so you do not need the DVD capability of Xbox. The GameCube being only £130, cheaper games, and being Nintendo would be the best choice. Nintendo and Rare(creators of Goldeneye and Perfect Dark) are some of the best developers in the world.
The line-up of games for the GameCube is looking good also:
-Perfect Dark Zero
-Die Hard Vendetta
-Resident Evil (already out in US)
-Eternal Darkness (already out in US)
-Super Mario Sunshine
-Mario Kart
-F-Zero
-Super Monkey Ball 2
And these above are just future releases, there are already loads of great games out for the GC - Super Smash Bros. Melee, Star Wars:Rogue Leader 2, Luisi's Mansion, Super Monkey Ball, Pikmin, Wave Race:Blue Storm.
There isn't another console with a line-up that is that good.
The all mighty god game "Halo" you are all talking about has now been given a PC release date, when will you ever see a Nintendo game officially released on the PC - never. Nintendo have also released information that they are releasing both dial-up and broadband connectors.
The GameCube controller is the best ever created, the design feels 100% comfortable. The Playstation controller isn't good, but the Xbox controller is awful, the designer should be shot.
The only reason I would buy an Xbox would be to lose Microsoft money selling it to me.