Personally, I think that butt biting isn't kiddy at all. But y'know.
Back to the point, I disagree with your opinions because you haven't given us any examples.
I think you're passing the wrong judgment, there's some people who want more games that are, crap, to be quite frank, games like Grand Theft Auto do not appeal to me in any sense. Who do games 18+ appeal to exactly? Do you have fun virtually demolishing a virtual world that will repair again and again? This is a monotonous sense of gaming, I hate it.
Nintendo offer variety in their games and a lot of them are actually quite difficult. Zelda is not a kiddy game, at all, it had a 7+ rating because there isn't exactly any gore in the game, and if there were, this would reduce it's aesthetic appeal and with many many villains around you're obviously going to have a red splattered screen. Do you really think that a kid could navigate their way all the way through those dungeons? No, of course not, these games involve some sort of thinking.
Manhunt was banned for a reason, and I really like the fact that Manhunt was banned because back in the Manhunt era when I was little all the kids would be out playing it, and destroying our grounds, and injuring themselves. It's inevitable that 18+ games will seep into the minds of children, with all the underage smoking and drinking these days it's bound to happen. They just have no idea how this could influence them and they may get it through peer pressure.
Parents have no idea what games are about, well, most of them, they obviously don't think that anything on a screen could affect their child in any way, it just gives them a bit of peace and quiet. They should read a bit more into games that they wish to buy their children.
Nintendo are getting by with their online play, it will soon come in to place where everyone will be connected to the internet facing eachother on Smash Bros Brawl. But until that day there's still some developing issues. You obviously have no consideration on how long it takes to set up online play within a game, think of all the things you have to do, it's basically re-designing the game all over again.
And as for their use of friend codes, I think that this is a good thing as well, I'm sorry if you want game developers that don't want to make the world a better place.