I never played nintendo games and consoles much, never owned one. In fact I'm not the game type of guy, I have a PS2 with at least 3 cms of dust on it, It was a gift, I played for a week or so and got tired of it.

But from what I see from friends, people who use different kind of consoles, it seems that nintendos are more user friendly. Just play and enjoy.
To me the gameboy and then DS line is exactly that: choose game, poweron, play.
You don't have to go to BBSes for hours, you don't need to know anything technical.
Games do not offer your gazillions colors or FPS... but some of them are very funny and entertaining... yes, sometimes console maker tend to forget that very last point.

And I find it clever of nintendo to target older audience and women, because the potential market is both richer and greater. If they can go there, they should be kings of the hill for long enough before others think of ways to follow them.