After Nintendo has the next generation of handhelds pretty much locked with the 3DS, it got me thinking about how things will play out on the home console side and it looks like Nintendo is going to stay on top for a long time there too.
Ever since Nintendo entered this business with the NES and re-established the video game market, there has been some sort of counter culture. For example, "Genesis does what Nintendon't". The competition defines itself as being "not Nintendo" while Nintendo obviously is "Nintendo" (at least most of the time). While Sega got eventually pushed out of the market by Sony, Microsoft reached parity with Sony due to their much deeper pockets.
As long as both Sony and Microsoft stay in the market, neither one of them will be able to beat Nintendo, because the counter culture remains to be split up between them. This counter culture traditionally consists for the most part of male people aged 13-25. It's this age group that makes it necessary for Sony and Microsoft to continue to make more and more "mature" games with the most imaginative and violent ways to kill things.
Many of the biggest third party hits in today's market are also targeted at the same demographic, so Sony and Microsoft will take care to not lose any of those games to the other company. Which means that their next consoles will again be very similar, because neither one of them would want to run into the risk of ending up with a Wii, a console that most third parties pass on because it requires a different approach to make successful games.
Third parties basically want to do things the same way, they are against change. And since Sony and Microsoft want to have third parties on board, they won't want change either. Neither do most of Sony's and Microsoft's main demographic, other consoles becoming like Nintendo is the last thing they would want to see.
All that leaves the ball in Nintendo's court. If they continue to be "Nintendo" they should be fine. However, if they try to become "not Nintendo", like in the Nintendo 64 and Gamecube eras, they will be facing trouble. During those two generations Nintendo tried to sell to the 13-25 year old demographic and we know they failed. But by doing so they also lost their previous fans, because they ceased to be "Nintendo". No 2D Mario, the mother of all killer applications, for two entire generations. This among other things made Nintendo almost slide into complete irrelevance.
But now with two giants fighting over the counter culture and Nintendo being "Nintendo" again, it's unlikely that either Sony or Microsoft will take the crown in the foreseeable future. Both are stuck in their box and trying to break out of it could mean ending up being left with nothing. A risk that probably neither one of them is going to take as gaming is their gateway to get the center of the living rooms in the world in order to sell more than just video games.