If a game is good, PLAY IT. I remember sitting in school playing Kingdom Hearts: CoM and eventually go over a firends house to play some Timesplitters 2 or Smash Bros. Melee and go home to play some Doom 3 or Katamari.
There are plenty of "kids" games on any other console out there (look at PS2) but they were never as common as the GOOD games.
Nintendo's had a reputation for making products for children as long as I've been on the net, and I've always maintained that they make games that are appropriate for children but intended to be played by all. There are honestly very few games that are truly marketed towards adults, anyway. Graphic violence being synonymous with "mature" in the video game lexicon is perhaps this art form's biggest stumbling block to being taken seriously. I think if that's what someone means by the system lacking adult games, then they have a fair point as there aren't many violent action games for the system, but it's not a huge detriment at this point in the system's life cycle.
"Critics who treat adult as a term of approval, instead of as a merely descriptive term, cannot be adult themselves. To be concerned about being grown up, to admire the grown up because it is grown up, to blush at the suspicion of being childish; these things are the marks of childhood and adolescence. And in childhood and adolescence they are, in moderation, healthy symptoms. Young things ought to want to grow. But to carry on into middle life or even into early manhood this concern about being adult is a mark of really arrested development. When I was ten, I read fairy tales in secret and would have been ashamed if I had been found doing so. Now that I am fifty I read them openly. When I became a man I put away childish things, including the fear of childishness and the desire to be very grown up."
IDGAF. Most of the time people who use 'for kids' as an insult are either insecure with or overestimating their own maturity. There was a thankfully brief moment in my teen years where I fell into the trap of thinking 'kiddy' stuff was bad, but now I play/read/watch whatever the heck I want, instead of whatever I get told is popular. If a game I like happens to be popular with 'my demographic', so be it. That's not how I determine a game's worth.
https://www.youtube.com/watch?v=KQ9Km7WW2aE Best console war summary ever. TL;DR version at 2:05.