Arguing this library is better than that one is ultimately so subjective. I think if you prefer more traditional Nintendo games to open world stuff, you could make a very good argument that the Wii U had a better first party library a year in than Switch 2. I have Mario Kart World. I don't play it. The open world means nothing to me and I don't care for it. If you like it, cool, but ultimately I had a lot more fun playing Nintendo Land, Super Mario 3D World and NSMBU when they were new games than I have with Mario Kart World.
If a game got a port to Switch you are better off playing it there (or even on Switch 2) than on Wii U unless you really like the original last two levels of Captain Toad.
I mean, not really.
Mario 3D World and NSMBU are totally better on Wii U. Bowser's Fury excellent, but the Mario 3D World port itself is atrocious. It runs too fast, and all the touch screen elements are mapped to motion controls when playing multiplayer in docked mode. NSMBU makes it so you can't play four-players without someone having to pick an easy mode character. You get Toadette as a playable character, but you lose boost mode, which I mean, make of that what you will.
I've played through BOTW on both Wii U and Switch. While there are more frame drops and lower resolution on Wii U, the game only looks negligibly better on Switch. When you put them side by side they're almost identical:
The rest of the Wii U ports have some stupid feature no one will use tacked on to justify charging full price for near decade old games like the ability to be Funky Kong in Tropical Freeze.
Now I'm not going to argue these were all
better for Wii U, because Switch introduces portability, but if you already had a Wii U or didn't care about portability, there was little advantage to upgrading to the Switch version of most of these games and you may as well have just played them on your Wii U. The Switch just introduced them to a wider audience because the Wii U install base was so small.
I think the one that is genuinely better for Switch was Mario Kart 8 Deluxe because it included the DLC and fixed battle mode, not to mention the DLC that came later.