If Nintendo made a mature game, and it sold gang busters, then this would give 3rd party more hope and may just convince some to give it a go.

There is a problem though with Nintendo making a mature game, and that is that with a mature games you are targeting a specific audience and this limits the sales, the reason why games like Mario kart and wii sports resort sell so well is because their for everyone so the target audience is the whole install base and not just a portion.

Although GTA game (3D, not the top-downs) show that portion is still large.

Yeah to me its not even about M rated anymore, people have lost faith in 3rd party. Even RE that sold amazingly well back in 2007 can barely do the same now. They just left it too late, their support is weak, and nobody tried to really produce a big Wii title that can succeed out there. The only huge franchise that has recently been a success is CoD, and thats because they've constantly put in a bit of effort(if it qualifies as an effort). And of course M-rated titles will struggle more since they've left a huge gap for the userbase

Every time Nintendo goes the 'edgy' or 'hardcore' route, they get mixed results or it even bites them in the butt. Look at Metroid Prime. Many people consider it a success, but is it really? It pretty much sold like every other Metroid title, only good in America. Or how about Twilight Princess. A title tailor made for those who focus on graphics and story over gameplay (pretty much the western gamer of today). And it was considered by some to be Nintendos poorest Zelda as of late.

And must we bring up the N64 and GameCube, which focused on graphics and trying to cater to the 'hardcore' market?

Yeah...Sega, you had your chance to make some 'hardcore' games for a Nintendo console. Instead, all you wanted to do was port Sonic Adventure for the third time and make weak games like 'Sonic Riders'.

This is just another third party whining about their games not selling because they didn't advertise them.

To all those on about Eternal Darkness... I have to ask, how are you supposed to move your character? the vitality sensor has to replace the nunchuck after all.

Hmm actually I suppose it could be point and click to move around, after all the old one did have relatively static cameras.

Why the N64 and GC underperformed is not because Nintendo was making "hard/core" games. There are dozens of other factors.

Obviously it was a test to see how much of their fanbase went to the Wii.  Whether it sold by merit or by fanbase, either would have been successful but it did neither.

Maybe Nintendo should combat piracy so some games sell better than they did (HOTD)

Sure there are dozens of other factors.  But if you look at the games many people (including reviewers) consider edgy or even hardcore on those systems, it didn't help push consoles are increase popularity of the system.  People didn't go out to buy 5 million new GC consoles for RE4 or Metroid Prime.  Or Ocarina of TIme and Goldeneye 007.  They sold some extra consoles, but most of the sales for those games went to people who already had the system or multiple consoles.  A problem Nintendo is having for the Wii now.

Nintendo sells more consoles when they make games that touch upon the 'all ages' or 'family' market.  Many people brand that as being 'non-hardcore', but just because Nintendo makes games for all ages doesn't mean some of their games doesn't also target long time gamers, like Zelda, Mario or Metroid.

yes, but they never DEVELOPED a single one