Software doesn't sell hardware.

Advertising trumps all, and Gamecube had next to none. There was no "cool" factor to owning one. Kids preferred halo parties over mario parties, and sony had all of the well known franchises under its belt.

I think selling Rareware had a lot to do with it as well as the other reasons stated. The N64 did well primarily off of the 1-2 punch of Nintendo and Rare. I am aware that Rare has since gone down hill in quality, but I really think they helped a lot during the N64 era. Nintendo could work on their bread and butter games, while Rare could make masterpieces such as Banjo, Conker, Blast Corps, GoldenEye, Perfect Dark, Donkey Kong, Diddy Kong Racing, etc. When Nintendo sold them ti was pretty big news all over the message boards and video game websites back in the day for a reason. Newer teams such as Retro has filled in nicely, but just do not put out the games quick enough!!

This is false. Nintendo made as much money as the PS2 when you combine the GCN and the GBA. GCN did make a profit, but not anywhere near what PS2 made.

Nowadays DVD players are everywhere, so it doesn't matter as much to people. Most people have 4-5 in their house. They're located in PC's, laptops, cars and even The Terminator's head.

No, Nintendo made more money on gaming every year during the PS2's life except for 2003.  Most years, Nintendo made around double what Sony did.

http://www.vgchartz.com/forum/post.php?id=1700495

nintendo had a more supporting demographic.
yet, third party sold tons on the ps2.
demographic it's split for both ps3, ps2. ps2 didn't had that many 5+ million sellers but got tons of million sellers
ps3 it's also that way, and also have main focus on online gaming, people spend hours in COD4 without having to buy many games.
ps3 have less time in the market than the GC it probably be pass it software sales easily.

ps2 and some other small things

It has nothing to do with third-party support. It has little to do with the DVD player.

It has everything to do with the "simplicity" approach Nintendo took.

Nobody wants a system that does NOTHING the competition doesn't already do. Everything the Gamecube did, either the PS2 or the Xbox already did. It had nothing unique to offer, except Nintendo first-party offerings.

The PS2, however, offered an earlier release date, a DVD player, and larger games, which, yes, resulted in a greater library in the end, and more third-party offerings. But it ultimately began with their earlier release date and the momentum created thus.

The Xbox offered DVD playback as well, greater power, the first heavy-duty online service, and a hard drive out-of-box.

My mistake. That chart was what I was looking for and couldn't find. Going off of memory probably wasn't the best idea.

No idea, what comes to mind is the fact that it might have been seen as a kiddie console as opposed to the PS2/XBOX.
It is a great system with a good group of exclusives but I don't think it is fair to compare it to the Wii. The Wii sold a lot because of motion control. if the GameCube had the same motion control with the same games then it would have sold a lot imo.