Great post, but I will turn C.S. Lewis on the head to prove my point. Did he ever considered children as vastly different than adults in that they could just no comprehend adult concepts?
The children in Narnia couldn't understand why adults concerned themselves with needless things. That would be the likes of the pulp we are fed like the GoW games or the Batman and X-men craze and reboots, ad nauseam. I'm not talking about that adult. I'm talking about adult that children and adults alike can enjoy, case in point, like Chronicles of Narnia, an excellent example.
This isn't just personal opinion, I know there are others who feel as I do about Mario.
and yet clearly there are more people who feel otherwise, hence it's sales. So it is really more of a personal problem. I mean, bad example, but i know more then one gambling addict. It's still a personal problem each person grips with.
Heck, look at all the internet love with the bronies. As far as I can tell it's unironic, actually watch and enjoy said show like mostly.
Mario's childishness is really part of it's charm at this point. Bright colors, ineffectual funny villians, the atmosphere more or less replaces what a deeper story normally would.
I don't see any difference between say Mario or Phineas and Ferb for example. Tons of adults enjoy that show. More then kids I think.
Mario IS the kind of game adults can, and do enjoy. Just not one you personally enjoy.