Nintendo is like you said in your OP, the Pixar of game developers. They make games that universally appeal to all demographics, are mechanically pretty simply to understand and good.
Look at Microsoft's biggest franchise - Halo. It's good but might be a bit unapproachable for people who don't have experience playing FPS. It's also not age appropriate. I would definitely not introduce a child to video games with Halo.
Then you look at some PC franchises like Civilization. Certainly a great game and all ages appropriate but it's not a mechanically approachable game. I mean, I would be ecstatic if an 8 year olds started playing Civilization on their PCs but I don't expect them to be able to pick it up.
Nintendo has many franchises that hit on all three major qualities: All Ages Friendly, Mechanically Approachable and Good games. Mario, Zelda, Donkey Kong, Pokemon, Kirby. Metroid might be the only franchise they have that doesn't fall into this category. Anyone can pick up a Nintendo game, identify the characters and learn how to play within seconds.
I think a lot of modern video games have lost that.