It's not uncommon for people to say that Nintendo only makes games for kids, and that the Mario games in particular are kid-only experiences. For instance, Blur, an upcoming "realistic" racing game featuring missile launching race cars and giant explosions, has a new commercial that's all about how Mario Kart isn't for "big boys". That may or may not be the case, but what about "old men"? What games are for them?
Well, according to Shigeru Miyamoto, a +50 year old man, Mario games are made for him, and people like him. He states that Mario "wasn't a game only for children in the first place" and that when he makes a game he tries "to keep in mind that guys in their fifties will play it, too."
I've long been of the opinion that most people that don't like stuff because it's too "kiddie" are insecure adults, or are in fact kids themselves. Only kids and teenagers think smoking is cool, or that a games is truly "mature" just because it's rated "M". Most of the adults I know that smoke are quite desperate to quit, and would much rather play Mario Kart than Modern Warfare. As for me, I like Modern Warfare and Mario, but if I had to choose one over the other, Mario would win hands down.
I can't hang with Yoshi's Story though, but not because it's too kiddie. It's just sort of nauseating.