Why so little third-party support for Nintendo?

I love video games. In fact, I believe you could call me an otaku of sorts in the world of gaming. I play games virtually every day and I have an incredibly large backlog of games to get through eventually. One thing about my gaming habits that’s notable, though, is how I’m a bit of a Nintendo fan. I have a SNES, N64, Gamecube, Wii, Gameboy Color, GBA, DS/DS Lite, and my brother owns a 3DS. The only consoles we own that aren’t Nintendo-made are our PS1 and PS2, and we have barely any games for those. Because I’m not exactly a connoisseur of games besides the ones released for Nintendo’s systems, I always got rather upset when people asserted how the Wii “doesn’t have any good games” or how the Wii’s selection was “lacking”.  I have a rather large library of Wii and Gamecube games, so I naturally took offense to this claim. Today, due to boredom, I decided to do some research on the claim instead of the supposedly unfounded assumptions of the other gamers… and it ends up that I was somewhat wrong.