This topic is freakin' amazing.
After I've read all of these responses, I had to look back up and check the subject again. And now I know the answer. Hear me out.
The root of all evil is "excessive fanboyism". All three consoles have them. I just laugh when I read responses on other console boards, and most recently this post. All I can picture is a bunch of kids jumping around on a playground screaming "mine is better than yours". Freaking hilarious. And sad. It's like people have to "justify" what they have by pointing fingers and saying, "I hate yours because..whah wha wah whaaaahhhhhh wahhhh waaaaahhhhhhhhhhhhhhh (In my best Charlie Brown's teacher's voice).
I've been a member of a popular Xbox board for a long time. Since 6 months before the Xbox release. Nothing makes me more sick than to hear "excessive Xbox fanboys" speak out of their arse. Putting down other systems, games, etc. Excessively promoting the Xbox like they are Bill Gates' biatch. It's almost funny. But it's easy to get sucked into thinking like one when an "excessive fanboy" from another console says something like "The only good game for the Xbox is Halo", or "Xbox sucks", or "I won't buy an Xbox because of Bill Gates". That is my personal favorite. Also on the other side, "GC is for kids, wah wahhh wah wahhhhwahhhhhwahhhhhhhhhhhhhhhhhhhh"
I am an Xbox fanboy. Not excessively though. I don't blindly promote the Xbox to no end. But I do promote its' good points when necessary.
Good things:
They have a pretty decent library of quality titles.
Proof?
1) Halo....Best....FPS....Ever. Don't knock it until you play it in HDTV with Digital Surround pumping out all around you. Amazing.
2) Apex...great racer, great grapics, great tracks.
3) World Racing...one of the best racers I've ever played. Awesome graphics, very realistic handling, custom soundtracks.
4) Buffy the Vampire Slayer....great hack 'n slash title.
5) Steel Battalion....simply amazing. You have to play to believe. Fabulous replays that are saveable on the HD.
6) Deathrow...awesome "future sport" game. Has a huge cult following.
7) MotoGP....great Xbox Live racer. Nothing like competing with 15 other people, and being able to talk smack with all of them.

Mechassault...decent single player experience...great Xbox Live title.
9) DOA Extreme Beach Volleyball.....just kidding....personally, it sucks.
9) Morrowind...very deep RPG. Not turn based (which is ok), but TONS of options, armor, weapons, races, cities, etc.
10) Kung Fu Chaos...with 4 players, this game is great fun and is hilarious. The replays are priceless.
11) NHL2K3...nothing like playing some hockey on Xbox Live.
12) Panzer Dragoon Orta...BEAUTIFUL game. Very challenging. TONS of unlockables, including more missions and the original PD game.
13) Quantum Redshift...Great playing futuristic racer with a crappy storyboard.
14) Shenmue II....the sequel to one of my most favorite games.
15) Tao Feng...finally a fighter that makes you learn the combos to win. Very strategic. Button mashers need to stay away...
And upcoming titles like Brute Force, Halo 2, Doom III, Fable, Star Wars: Knights of the Old Republic, Sudeki, Return to Castle Wolfenstein:Tides of War, and others, it looks like the future for the Xbox is bright.
Great Hardware with a lot of untapped capability.
Great customer support. There was a period of time where some Xboxes were failing prematurely. To this day, MS is still repairing a lot of defective Xboxes (or replacing) at no charge, no questions asked.
Anyway, that is my PRO list for Xbox.
Cons: They have a strange marketing plan, promise the world sometimes and do not deliver, put out some of the god-awfullest titles (Bruce Lee, anyone?) that should have never seen the light of day, and are like a neverending hype machine. Even Xbox fanboys are beginning to take grains of salt before just believing everything. Also, the Xbox is damn HUGE!!! I didn't really realize how big it was until I put my GC beside it. Holy crap. You could make 3 Gamecubes from the plastic from 1 Xbox.
I just got a Gamecube about a month or so ago. I have some good titles for it. A few, I'd put in the great column. I never really payed much attention to the GC.
And to be honest, I really didn't because of the "kiddy" titles. I wouldn't call them "kiddy" now, but that is the image some people get when they see Mario, Animal Crossing, Pikmin, children's games such as Pooh and Tigger (which my kids love), etc. You see where I'm coming from.
Some people are blinded by ignorance.
Once I got my GC, I went out and got 4 titles: Eternal Darkness, Metroid Prime, Zelda: WW, and Super Monkey Ball.
The next day, I went out and bought: Pikmin, Resident Evil, and found a used copy of Zelda

OT/Master Quest (bought all 3 for $35.00)
A week ago, I bought Rogue Leader and the Tigger/Pooh game for my kids.
So what's the verdict?
Freaking Metroid Prime has me hooked. Hooked on a game like I haven't been in a while. I didn't like it at first. But once I beat the Parasite Queen, it's all been sweeeet.
Zelda : WW is simply art in motion. Almost a perfect 10 in my eyes.
And I like the other titles too, just between MP and All Star Baseball 2004 for the Xbox, I haven't had much time to get to them.
Gamecube will always be in my home from now on. And when Nintendo's next console comes out, I'll buy it too.
Ignorance almost kept me from enjoying some great GREAT titles. Not being an "excessive fanboy" with blinders would have made me miss out on the chance to play probably 2 of the best games of the last 5 years (MP and Zelda).
I feel that "Excessive fanboys" from both sides of the console war would really appreciate the other console if they had time to invest in the other console. To call Xbox "crap" and not spend a few days playing Halo, Steel Battalion, Panzer Dragoon Orta, etc. should be a crime for a "hardcore gamer". Same goes for Metroid Prime, Zelda, etc. These are some of the best games of this generation.
In the end, just give me good quality games. I do not care by whom they are made. Whoever makes the best games is who gets my money.
That is why I sold my PS2, but that is another story....
Sorry for the rant....