Pokemon isn't really a great example because it's a massive outlier, a once in a 50 year type phenomenon that came out of nowhere. You can't really say "well see Wii, Pokemon boosted Game Boy 8 years after launch, why can't you do the same", like that's not a realistic ask for a software library.
The fact is even when the Wii had major releases like NSMB Wii and Super Mario Galaxy 2, the system still was on a sales decline.
I think XBox 360 getting Kinect also hurt the Wii, because really it stripped the Wii of being a unique system which the only go to place to play Wii Sports type games. All of the sudden you gave consumers a choice between one console that can play Wii (well Kinect) Sports + Call of Duty for the teenager in the house versus the Wii which had Wii Sports and didn't have the "real" Call of Duty.
For a mom trying to make her kids happy and wanting to have some bowling fun when the grandparents came over, by 2010, honestly the XBox 360 was the better option and also quite affordable. Instead of having to buy the Wii for Wii Sports/Fit and then get a 360 for your 13 year old, you could just buy one that basically did both things. For a lot of families I think once that option was presented to them it became more attractive than the Wii. Why buy two different systems spending several hundred dollars more when you don't have to.
I mean IIRC the XBox 360 very rarely beat the Wii in NPD sales prior to Kinect releasing, but after Kinect released they were no.1 on the NPD chart for the majority of the time. This is also the danger of banking so heavily on simplistic games ... that can copied eventually by other companies (Brain Training, Wii Sports, etc.). It's not so easy to copy Mario or Zelda or even Pokemon.
To be honest the Sony Wii Sports ripoff (can't even remember the name) was the best one from what I played. The controller was really accurate and felt like your movements were really accurately reflected on screen.
We're talking about Nintendo here. Don't ask me to give examples, the Wii itself was a knock-off hit.
Whatever Xbox and Playstation did, Nintendo was king in motion controls. They let the thunder slip out of their hands, it's really time to face the music.
The best you could argue is that motion were going out of style. In which case, again, this is Nintendo. They had knock-off hits in pretty much every type of game imaginable.