Go look at 360 vs Wii NPD pre-Kinect and post-Kinect. MS starts to win almost every month. What a magical coincidence don't you think?
There is no king of motion gaming because it's an idea that can be copied. It's like saying Nintendo was the king of brain training ... this is an idea now that has been copied in so many shovelware apps on smartphones and online websites that it's really not special.
Switch won't have this problem though because you can't copy a portable console with a full blown software ecosystem (no half assing it like Vita) as a concept very easily.
Anyone can make a brain training/brain teaser game or a sports compilation with bowling. The Sony bowling one was pretty much as good as the Wii Sports one from what I remember, the tennis was better.
So Nintendo should have made an EyeToy instead of the WiiU? Makes sense.
Don't Play Stationary 4 ever. Switch!