But what about the first party titles like Mario Kart and Smash which have huge attach ratio on the Wii U? Those games you listed on the Wii were a fad but the system itself sold itself quite well for a standard five year Nintendo console.

Mario Kart and Smash have a huge attach ratio on every Nintendo console. 

In fact if you look at the top selling Wii/3DS titles, basically all the new IP -- Wii Sports, Wii Fit, Mario & Sonic, Brain Training, Nintendogs, Wii Party ... all basically bombed in the successive generation all across the board. 

The only IPs introduced on the Wii/DS that are still big today are largely the pre-exisitng Nintendo IP that were already big before -- Smash, Mario Kart, Zelda, Mario, etc. 

All the so-called casual IPs are all bombing today. Not just for Nintendo either, MS banked hard on Kinect Sports for XBox One and it also flopped after selling big on the 360 just a couple of years prior. Rock Band sold so badly that the president of Mad Catz (the publisher) stepped down. 

I dont understand why the Wii is considered a fad? Yes sales slowed down in its fifth year, just like every other Nintendo console. If the Wii is a fad, then every Nintendo system besides the NES was a failure.

Because the audience dropped Nintendo like a sack of cold potatoes rapidly.

Also the dramatic drop off in many/all of these casual IP ... whether Wii Fit, Mario & Sonic, Wii Party, Brain Training, Nintendogs, Guitar Hero, or Rock Band ... the drop off has been unbelievable, they went from IPs that were selling tens of millions of copies to selling like 50,000 copies in some cases. 

Also things like Zumba Fitness and EA Active and uDraw which were successful on the Wii, their sequels suffered monstrous drop offs. 

That is pretty much a textbook definition of a fad. 

Then why are we calling the 360 a fad when the One is selling so dramatically worse? Although the Wii was sold primarily on those casual titles, it doesn't take away the fact that many established first party titles sold incredible well and have also helped moved the system including Twilight Princess, Mario Galaxy, Mario Kart Wii, Smash, and New Super Mario Bros series which was created during the 7th gen along with the rebirth of Donkey Kong Country.

Well......

maybe the Wii as a system wasnt a fad. But motion controls? yeah that was a fad

So every sega console and the original xbox and arguably the One is too because it will sell less than 60 million right? I'm talking about failure sale wise like Virtual Boy and Wii U and not as losing marketshare.

This is what I'm arguing for. Even if a system has a gimmick or games that were fad as its primary (but not exclusive) selling point, but it can survive for a typical console life span of 4-6 years with good sales, then that system is not really a fad. It simply had those things as its selling point. If it did 20 million one year and crashed in its 3rd year while the competitors kept on outselling it, then the system is definitely a fad.

It's not the gamers who decided to take "the blue ocean strategy".