What Nintendo systems has Switch already surpassed for you?

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Wii U games may have helped fill some gaps while Switch established itself, but that's frankly just par for the course since the start of the 8th gen, Xbox and PS do the same.
Even in 2017 Switch had plenty of content not on Wii U, from Mario Odyssey, Xenoblade 2, ARMS, and Kingdom Battle to Doom 2016, Rocket League, Skyrim, etc. Splatoon 2 is also very much its own game and doesn't really reuse much more than most iterative sequels.

We're way passed the point of Wii U games making up a substantial share of the lineup, and ever since third party support kicked into high gear around 2019 we're once again in a position where games from third parties fill the spaces between big Nintendo games.

If you stripped out all games from prior Nintendo systems, Switch would still be second only to the SNES I'd say.