I don't see how this is more (or less) mature. Metroid was plenty mature. The world it takes place in is sophisticated, the gameplay goes beyond simple "shoot-em-up" involving puzzles and maps that are more mazes than anything else. The art style, too, was very mature. This game looks to be equally mature.
(Disclaimer: I don't think maturity has anything to do with how good a game is. No More Heroes is pretty immature, but it doesn't try to pretend otherwise and it rocks.)








