Yeah I know Mario might be an exception but these sold gangbusters on the Wii, and even on the Wii U they've hit at least 2 mil each on a console on life support. I also expect Tropical Freeze to at least sell 1 million, maybe more but I could be wrong.
IMO Rayman's tepid sales are solely Ubisoft's fault. If they had orgiinally released the Wii U version in February, they probably would've sold at least a little more, because there was absolutely nothing to play on the Wii U. Then, they could've used that revenue to continue multiplatform releases. Instead, they push it to September, where there were probably more platformers on the Wii U coming out than shooters on Xbox/Sony. Plus, they decided to release all versions in GTA V month, so they kinda shot themselves in the foot.
I won't go through the rest of your list since there's too much there but I somewhat agree with you otherwise. I don't agree platforming is niche, just that there's so many good ones (as your list shows), that the market isn't big enough to support them all. It's not the shooter or sports genre but if there were fewer platformers a year I think they could each be at least million sellers. The problem is again, there's too many, even though most of them are excellent.
As a side note, slightly controversial opinion, but there are probably so many platformers because they are easier to make than most other genres. They don't require sophisticated enemy design or multiple weapon/abilities or even enemies at all, and require less resources. Platformers can succeed based solely on interaction with the environment.
HOWEVER, that means that the controls have to be fluid and precise, and the level and environmental design have to really wow people. The design has to be difficult, so the players don't get bored, but fair so they don't quit out of frustration. So making a GOOD platformer is very difficult, and is even more difficult to design than other genres in some cases.
