Gore, violence and swearing do not make a mature game.
If anything, I'd say a game that doesn't have to resort to putting those things in excess whilst not being patronising is a mature game. And Nintendo make those in spades.
"Beer is the mind killer. Beer is the little death that brings total obliteration. I will face my beer. I will permit it to pass over me and through me, and when it has gone past I will turn the inner eye to see its path. When the beer has gone there will be nothing. Only I will remain."
Make beer, not war.