Unless you know a bunch of people who have Xboxes, Halo, and a spool of cat5, pass. Halo's PC port wasn't that good, but it wasn't that good of a FPS period. The novelty of Halo is that it lets you play games with more than 4 people. Since the PC has had that for ages, with vehicles, in much better titles, Halo is very much redundant.
It also had rather lackluster singleplayer.
Throughout, it seemed more like they were attempting to create a "futuristic warfare" simulator rather than an entertaining first person shooter. They could take a few lessons from id - at least their games were fun, and their maps weren't just the same hallway model pasted in 5000 times.
No... really. There is very little in the way of selection on the Xbox. There are absolutely no exclusive titles to speak of. It has a very small library, and an even smaller selection of quality games beyond that.
I've heard of one GCN title that had serious bugs. I'm not talking about instability, I'm talking about game breakers or serious errors in gameplay. That one title? A sports title.
Off hand I can think of two major games that have suffered from gameplay bugs... Kotor had a game-breaker that a couple of -ites ran into. Morrowind suffered from the usual spattering of bugs that made their way from the PC version. I'm sure I could find more if I tried looking.
Regardless, the fact remains that many of the people who buy the Xbox buy it because of its multimedia capabilities. In order to get those capabilities, you have to buy a special remote. The PS2 comes with that ability enabled. The remote isn't required.
The US release of the Gamecube was about a week after the US release of the Xbox.
The Xbox is also the most expensive of all 3 consoles, which its library cannot possibly warrant.
The only remotely good "exclusive" title, Kotor, is now available for PC in all of its patched glory.
The Gamecube's library has finally matured. There are games to choose from, and so many that - for a change - I'm not able to buy all of the games that I want for the console. The Xbox, on the other hand, isn't in a better position now than it was when the console was released. Halo still tops the 'must buy' list for Xbox buyers. I can't name a single launch title that I'd recommend to a new Gamecube owner. Pretty pathetic.
And to top it all off, the Xbox has no franchises. None, at all. Microsoft has been cannibalizing the PC game industry for their console, and it goes without saying that the PC game industry doesn't have any of the franchises that console gamers look for.
All of this, combined, is why the Xbox is currently a distant third in the market.