It's this article. Again. That I see every single generation, both portable and console.
It's this simple. Nintendo knows it's power exists in first-generation titles, and it will never publish its A-list properties on other consoles. And as long as they don't, they will never fail.
I'm sure someone will, or already has, argued the VirtualBoy against the idea of Nintendo's continued success, and of course there's some merit there, but lets be honest, they were simply ahead of their time. After all, here we are a decade or two later, and what's the rage? A true 3D portable.
I could also argue that they're basically the only company still creating/publishing games that still hold to the old premise of gaming: that games should be fun - but that is admittedly opinion. And yes, I own a PS3 and an X360 - they are entertaining, in their own right. But none of their titles seem to induce that giddy Saturday morning feel of childhood quite like a Zelda game, or Smash Brothers.
Add in the fact that Nintendo produces the most polished and least buggy titles on the market, and... yeah. I think I'll buy a Wii U. Sony and their flat out abuse of their user base, and Microsoft and their pouting over 3rd party sales - can take a next gen dive.