I think where Nintendo tends to have longevity and win out on hardware that is not "cutting edge" is that the company's focus isn't entirely on the "hardcore" adult gamer. They are usually cheaper than their competitors, and combined with dependable franchises appeal to gamers who will play whenever they can, namely kids.
Zetr0 accuses me of being a fanboi for Ninty because I have all of their consoles, and when I think about it, he may be right, but I don't froth at the mouth about them. However, their systems and games are good, and I have so many of them set up permanently because the games are fun to play.
They maybe overshadowed in the eyes of some gamers by their Sony and MS contemporaries, but Ninty are still here, and are likely to remain for a while.
I would also argue that, you could probably lose either Sony or MS from the market (but not both) and TBH it wouldn't affect the market very much. Losing Nintendo would mean that the gaming world has changed dramatically, primarily because of the market they target, families and young gamers. If young gamers are no longer interested in consoles, then eventually Sony and MS will be in big trouble too.