I've never gotten why the gamecube is considered such a failure. I mean sure, it sold nowhere close to the ps2 (but then, besides the DS, what has?), but sold nearly as much as the original xbox, had an amazing controller, and some awesome games.
Gamecube sold around 22 million units, while close to Xbox sales, it's the Nintendo console with the least number sales(excluding WiiU, since it can't be compared now).
Even Nintendo 64, the 2nd least selling Nintendo console and it's predecessor, sold over 11 million units more than gamecube.
Considering Video Game sales tend to grow over time, it's fair to consider Gamecube a failure in terms of sales,
especially considering it concurred with PS2, one of the most selling consoles of all time.