From a marketing POV I'd have turned the tables on Sony/MS.

Instead of marketing with men/teenage boys in their commercials primarily I'd market with celebrities. Megan Fox, Zack Galafanakis, Psy, that sort of thing (whoever was hot circa 2012). I'd aim for commercials that are funny/cool. 

I'd take the piss out of "hardcore gamer" and reposition them as the nerdy type, just as Apple successfully repositioned Windows PCs are something for squares. I'd push XBox/Playstation as the brand for nerdy teenagers who don't have girlfriends and neckbeard types who live in their mom's basement still collecting comics. I mean yeah, it's tough, but I'd do it in a loving tounge in cheek way. Poke a little fun at the XBox/Playstation "dudebros" culture. 

Plus it'd make the commercials more fun, and that's more in tune with Nintendo anyway.

gta fans are conditioned to buy it through marketing. it's just a franchise that got lucky.

nintendo games have the game and level design that make them trully different than their predecessors. even when there isn't that much difference between a game and it's predecessor, at least it's been a while since the previous game.

And yet Windows still does pretty well overall. The PS/xbox isnt just dudebros, its people who like video games PERIOD. Thats why they are putting up the numbers in the speeds they are doing. And I doubt Ninty is going to pay celebs that kind of money, they barely want to spend for advertisment.

The thing is even if they did position PS and xbox as something for nerds, what would that change? isnt that how video games were seen for a while? Its not going to stop those nerds the ones who will buy things consistently from buying those systems and its not going to get them to buy Ninty and its not gonna have the casuals come back

I'm still waiting for examples

How about the very first you complained about? super mario kart started it all, mk 64 brought the series to 3d, super circuit brought the series to handhelds, double dash had the two characters per car mechanic, mk ds and mk wii brought online for both handheld and home, mk 7 had the gliding and sub aquatic section, and mk 8 had anti gravity while perfecting everything from before (except the battle mode).

the nsmb series don't differ much in mechanics, but when there's only one per system and each of them is composed by dozens of unique levels, one can't say they're too similar.

Why does it matter that Windows still does well? U act as if Nintendo has to push PS/XB out of the market, which they dont.

"I doubt Nintendo is gonna pay celebs that kind of money". Another point that makes no sense, this thread isn't about what Nintendo will do, it's about what they should have done so that statement was useless.

Sega found alot of success in the early 90s by labeling Nintendo devices as being just for kids (which wasnt true) and by making themselves seem like the hip/cool brand. Poking fun at PS/XB and using the most popular celebs at the time could potentially lead to Nintendo finding similar success.

the core gameplay remains the same. Are those things you listed really changing the gameplay that much? Cause that is what you were arguing and how is that any different than other franchies that have multiple entries? Heck the changes in a AC series are just as much if not more than those you list of Kart and are you really going to say Ninty is the only one changing it up?

So because they are on different systems that makes them unique? that doesnt make sense.

I never said they had to push them out the market, so i dont know where you're getting that. He suggested thats what they should do to get some market share back i just gave reasons why that wouldnt work.

IMHO i dont think Sega is a great example considering how crappy the sales of their consoles have been in general. Genesis was the only good one and evne then it trailed behind the SNES. Youre giving celebs too much power IMHO, people arent THAT gullible.

Segas success was founded on the weighted bias of gamers wanting to associate more with adult / grown-up games than "kiddy games".

Nintendo can't poke fun at XB/PS using that same tact, or they will look stupid, nor can then try to use "haha look at those stupid adult games, kiddy games are where its at" because the general populace still much prefers adult oriented games as a large majority.

Getting celebritys to help try and sell the system as "cool" wont work, celebrity endorsements for the most part only work on something that was relatively popular to begin with, something the WiiU is not.

As an original Grand Theft Auto player, I disagree with your sentiments.  They produce quality titles which speak for themselves.  I haven't liked them all equally, how can one, but they take a good formula and consistantly expand upon it.  Nintendo does the same thing, but as it has been mentioned numerous times in this thread, marketing could have been better for their sales.  I wouldn't call it a failure though, even in reference to sales.