Ok...first of all...it matters not how the game looks...it's how it plays.
XBox IMO is a hunk of junk. There's barely any games on it that are worth playing besides maybe Halo, Rallysport, and DOA Extreme Beach Volleyball. Microsoft could have done so much better with it than they did. Granted, XBox Live is good, but it still has its quirks. I do not like having a PC sitting in my living room.
The PS2 right now is one of the greaest systems on the market. It's got good games, a huge selection, and decent looking graphics if you're into that. If anything, I'd go with it simply because it has the largest selection of games. Sony came out ahead of everyone in this console war due to the fact they launched a year before Microsoft and Nintendo.
The GCN is NOT...I reapeat...is NOT a kiddie system. I don't give a damn what anyone thinks...it is not a kiddie system. There are only three reasons why people think GCN is kiddie...it has a handle...it doesn't play DVDs...and Mario. Nintendo did what they've always done...made a GAME console. It is not a set top box...it's a game console. That said...it also has one of the best playing games of all time. Super Monkey Ball, Star Wars: Rogue Leader, Resident Evil (all 4 including Zero), Legend of Zelda: The Wind Waker, Super Mario Sunshine, Star Fox Adventures, the list goes on. Granted, the system is lacking in the games department, but Nintendo knows what they're doing...they pulled the video game market out of it's crash back in 85. Those who think the GCN is kiddie...get yer heads out of yer arse.
Overall...PS2 is your best bet...give GCN a try...you might like it...