Personally, I thought Nintendo did address a lot of it's problems from the N64 era. It made a lot of mistakes too, but think about it. The single biggest problem with the N64 was a lack of third party support. We were going on about one game per month in the system's first and last years, and the system ended with about 250 games. The GameCube already has more than 400 games to choose from and although third party support is waning, it's still about as good as the N64's third party support was in its very best years.
Then there were mature games...Nintendo helped bring us Metroid Prime, three basically new Resident Evils, Eternal Darkness and Metal Gear Solid: Twin Snakes. We've also had a decent selection of multi-platform mature titles, including most of the Tom Clancy games (blech), Prince of Persia, Timesplitters and an assortment of others. It isn't as big as the selection of mature titles on the other consoles, but Nintendo did put a in serious effort and I'd say that it improved on the N64's selection.
Leaving us with RPGs. The GameCube is still no RPG powerhouse, but with Paper Mario and Ogre Battle 64 being the only great RPGs on the N64, I'd say the GameCube has easily beaten it. American RPGs are rare on the Cube, but then again, they're rare on all consoles except the Xbox. If you want Western RPGs, you should be playing PC.
Things improved a lot on the GameCube. Nintendo screwed up here and there and the Cube lost a little marketshare, but I'm not buying Nintendo consoles to say I own the most popular system around. The GameCube provided a lot of great games, that's all that matters to me.
Ummm, hey, I'm totally off-topic. I think Microsoft is jumping the gun a little, but I also think that Nintendo and Sony will be a bit late if they wait past July 2006 to release their consoles.