Nintendo just faced legit competition at the beginning of the 5th generation. Pretty much anything Nintendo offered, the competition offered better. Better hardware, better features, better support. Nintendo had its amazing first party and exclusives but almost consoles have great exclusives.
Since 1996, Nintendo has had two home consoles that can be considered smash successes (Wii and the Switch) and three that could be considered disappointing or failures (N64, GameCube, Wii U). The two successes were the two consoles that broke away from the norm in ways that struck a chord with the public. Nintendo's first party has always been spectacular. They're my favorite gaming company. They just can't compete with the other systems on their terms. They have to be creative.
Nintendo has made a lot of things standard in gaming. Probably more than Microsoft and Sony combined. Their first party games are the kinds of games I find myself going back and enjoying DECADES later just as much as I did the first time I played them. Even the games on their "failed" consoles.
From my point of view, their lowest selling consoles do have one thing in common: They were watered down versions of what the competition was offering instead of being their own thing.
