But GC does have a wider variety of games then just traditional Nintendo games. Check out what thread your posting in for just one example.
Of course there's more to Gamecube than Nintendo games. But not
much more, especially in comparison with PS2 and Xbox.
Ask yourself (or anyone else): What do you think of when you think "Nintendo"?
You think Mario, Zelda, Pokemon, Metroid. THAT's Nintendo.
"Nintendo" doesn't mean a huge variety of games from every genre. It means pastel-colored game worlds and cute, Italian plumbers with white gloves.
It's no coincidence that Gamecube, like N64 before it, lacks the third-party depth and breadth of its competitors. Simply put, Nintendo sells game consoles primarily as a means of
selling its own software.
That's fine if you're a hardcore Nintendo fan. But if you're not, it means a smaller game library that emphasizes colorful, Nintendo-made games and comes up lacking most everywhere else.
This is why I don't think the occasional "mature" title - even a monster game like RE4 - can trigger a sustained hardware sales lift for the console. People don't buy Gamecubes to play those games, because they're just too few and far between.