Nintendo wont be making any games for the Xbox in the forseeable future, especially since Microsoft has essentially just stolen one of Nintendo's most high profile development companies, Rare in a deal worth more than $300,000,000.
The PS2 has already won the console war in terms of popularity, with a sales lead over the Gamecube and Xbox of more than 11million units. There are a good number of great games for the system too. The PS2 is definately a stable and low risk investment for the the next 2-3 years before the PS3 hits us (rumoured to be in 2006).
The Xbox on the other hand is struggling at the moment and lost Microsoft more than $16Million in the last three months alone. However, they are determined to make the console a success and have the funds to support it. Additionally, as has been mentioned, the Xbox is considerably more powerful and it's got games like Halo, Jet Set Radio Future and Splinter Cell released for it, all of which are top games.
The Gamecube has Nintendo's genius behind it, and everybody knows that, whilst their games aren't always the coolest, they're always innovative and extremely fun to play.
As long as you don't mind waiting between Nintendo's releases, and being somewhat neglected (Japan and US get Gamecube games up to 6 months before they're released in Europe) then the Gamecube is well worth the measly �129.99 asking price.
Take an objective perspective on the situation, by doing that you'll be able to decide which console is best for you.