I'm not sure I understand the dichotomy you propose at the end; that if Nintendo didn't market to children, no other large publisher would?
Nintendo make games for families, as in, they think games should still be fun when people of drastically different skill levels—like a parent and child—are playing. Smash Bros has handicaps. Mario Kart has blue shells. Mario Party is skill-based over the short term but luck-based over the long term. It's all in the service of "having fun regardless of skill disparity." That's also why they make the only good "party games."
And Nintendo make games for themselves, as in, for example: they never make plain sequels (even Mario Galaxy 2 had new mechanics and a different level design philosophy) because that'd be unsatisfying to them as players. Nintendo is run by auteurs who care about inventing fun new game mechanics first-and-foremost, with the branding/license that those game mechanics should be "wrapped in" coming later in the design process. Strip all the aesthetic of a Nintendo game off, just laying the game loop bare, and each of their games is still unique.
One way I've seen this put is "Nintendo seems to have the vision of a bunch of parents, each imagining using these games as levers to enhance their time spent playing with their own kids." Nintendo don't make new games to give parents more of the same lever; the levers they produce already have replay value. Instead, Nintendo are trying to give you, as a parent, enough qualitatively different levers that you can find the one (or the several) that's a perfect enhancement to your individual family's bonding time.
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Now, Disney might know what makes an experience a family can enjoy (vis. movies, theme parks) but I think they follow a different philosophy, where the different people in a family will enjoy the same experience for different reasons. They create their experiences to have individual components that are individually satisfying to separate imagined user-roles, while being benignly ignorable to people who don't fit that user-role.
That works for a movie—it means that as you grow, your transition between roles will mean that the movie has rewatch value. And it works for a theme park—kids just enjoy the components for them, while parents both enjoy the components targeted at parents and vicariously enjoy the components targeted at kids, through their kids' enjoyment.
But I don't know if it works for games. A game that is actually a collection of separate layers, where any individual player will only connect with some layers, isn't going to be hailed as great pretty much anywhere, because the experience won't have been systematically polished for any particular user. Disney Infinity is not "for" anyone. It's for families, but it's not specifically for a particular player in the family, nor is it for the family as a whole in the way a Nintendo game is.
And, because Disney experiences are not really so much for connecting families together in a shared experience, so much as they are providing individual experiences good for each family member, Disney don't try to make games that they'd like to play—because that just means that they'd be biasing their production in favour of the adult experience at the expense of the child experience. So they just focus-group adult reactions, and child reactions, and maybe further split that into parents/not-parents, male/female, etc., and optimize for each of those groups' satisfaction with the experience. But in doing so, they further diminish the thing that makes a game that is "family-friendly" an attractive proposition.
(Disney did used to make some good, memorable games, mind you. In the 8/16-bit era, DuckTales and Aladdin were both excellent. I think this was back when they were forced by cartridge limitations to focus the experience solely on one hypothetical user—one "family member.")
Not sure which DuckTales you are thinking about, but the NES one was made by Capcom.
Frankly all the good "Disney" games first and foremost were mechanically good games that happened to be dressed in Disney characters.
The Sega Genesis version of Aladdin was actually made by Virgin Games.
Apparently from what I understand Sega secured the license for Aladdin and enlisted Virgin Games to do the development. At the same time I guess Capcom owned the general rights to publish Super Nintendo games with Disney characters, so they developed the own Aladdin game.
There's no argument that Nintendo pumps out some great games but its not like the west doesn't compete in the space.
The point being made is: if those Japanese games were absent from the market, we'd be left with the more bleak and violent US-made games.
Seems like a market hole would exist if we were stuck with "more bleak and violent US-made games", and I doubt your caricature of Americans would allow a market hole like that to exist. :)
An appeal yes, but also a cultural fingerprint.
Else we'd see Japanese and Americans doing those kind of games in equal measure.
If the example was with music, few would argue that Brazil and co etc would make more and better samba and the like than the US, or that the US will make more and better jazz or hip hop.
So why not accept that video game genres and styles can also be more cultivated in this or that area as well?
But we do. You might have been trying to say that American-made non-violent games do not have such massive success some Nintendo games do but what does it prove? It's about as same as claiming that Swedish music is culturally pre-disposed to saccharine pop because ABBA is the most popular Swedish band.
I think that's partially untrue as there are quite few indie publishers in the US, who don't produce violent games.