It depends on the generation.
In the case of the Wii/DS, there were more games sold on Wii, and more users of the console. This is because, while Wii sold fewer units, most units had multiple users. This isn’t the same as DS, it’s usually one console, one user.
In the case of the Wii U/3DS or the Gamecube/GBA, it’s that those two consoles were not very appealing. They had games that people liked, but no killer apps that made players want it over a PS2 or have players saying “this I have to have!” Also, both consoles were a little ridiculous/unappealing. With Gamecube and N64, it’s not that there were fewer Nintendo fans, it’s that the consoles had clear issues that made them unappealing when compared to the competition. First of all, with Gamecube, all the big games were on PS2. Meanwhile, thanks to Pokemon and a lot of RPGs, Nintendo fans were still buying the handhelds, but were substituting their N64s and Gamecubes for PlayStations. With the Wii U, I think a lot of people hung onto the Wii or got a PS3, and were more or less waiting for the Switch, rather than the Wii U.
The Switch has the benefit of giving everyone their own personal unit, but is also very open up to sharing with other users.
I think this opens up the big flaw with the Switch. Come 2018 and 19, people will be screaming for Family Share. This kind of console that has people who may start out on the same console before splitting, are going to want full access to the DLC and digital games they are accustomed to when they upgrade from using the Family Switch to having their own personal unit.
I describe myself as a little dose of toxic masculinity.
