It will be always worth buying the GC just for the Nintendo exclusive games. The N64 wasn't the disaster that many people thought it was, it is still the fifth best selling home console of all time and sold more than any Sega console, Megadrive included.
The GC will easily come in second in Japan and has sold pretty well, despite an average (by Nintendo standards) release list. When the big guns come in later in the year, it should really take off in Japan and the US at the very least.
X-Box will sell well in the US, but in other territories it may struggle.
The PS2 has "won" the sales war already and nothing can stop this behemoth now. As I've said before though, sales don't mean anything when it comes to quality and shouldn't affect a persons descision over which console he buys. All three will sell enough to have a decent level of support and more and more games are appearing on all three platforms nowadays.
Just get the one whos games appeal the most, or best of all get all three

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