Mario would never go around murdering innocent people.

They should use Luigi instead. That dude's fucked up.

Considering that Nintendo still faces that stigma after having Bayo 2, Mass Effect 3, Darksiders 2, Aliens: CM, CoD: BO2, AC3, and then Devil's Third down the road, I don't think this is gonna help much.

If that means so much to them, they should money-hat an exclusive GTA home console game. I'm thinking a GTA game in a setting so unique it demands people attention. Maybe Bangkok? Rome?

They may be looking to have Devil's Third, Bayonetta, and Project Treasure fill that role in the meantime though.

If Eternal Darkness/Resident Evil exclusivity for GameCube & ZombiU/Bayonetta 2 for Wii U couldn't get rid of the "kiddy" image than I don't think Hatred will have much success.

It would be a good idea but it definitely needs some Mario on it otherwise you will risk losing the Nintendo fans. A Mario with a shotgun DLC should be all it takes to make those sheep play the game.

You neglect ZombiU, Ubisoft's best selling mature game on a Nintendo platform, well... ever.

"Eternal Darkness" didn't do it for the Gamecube. Even paying for "Resident Evil" exclusivity for several years didn't do the trick. I think part of it has to do with gamers remembering the Nintendo of their youth, only to find the style of games they enjoyed then (Mario, etc.) "too kiddy" for their early teenage selves.

The funny thing is that I've seen this in myself and others, starting somewhere between 9 and 18 and ending anywhere between 12 and 29 (it's different for everyone).

Almost universally, though, by the time we hit 30 we stop worrying about whether or not our entertainment is for "grown-ups".

There's no better mark of lingering childhood than needing to put off the image of "adult". One would have to be a pretty serious dude bro man-child to still be worried about how "kiddy" his entertainment by the time he/she hits 35.

EDIT: Forgot to mention the fact that they've gone after both "Bayonetta 2" and "Devil's Third" this gen. Hopefully a third M-rated exclusive will hit before Nintendo starts shoveling the dirt on the Wii U. I have to admit that I do like a little more diversity in intended age group than Nintendo usually brings to the table... Then again, the same can be said of Sony/Microsoft. 

I "hate" this idea yar har har

Nintendo doesn't need more rated M games to look less kiddy. They just need to make their mature IPs well known and make more games for them. I think Nintendo's ventures into movies, theme parks, and smart devices will be a great opportunity for them to advertise their more mature IPs like Metroid and F-Zero.

I doubt a single game will save them.