This is my first Nintendo system since the NES. I've never been a big fan of their first-party properties when I've played on others' consoles, although I am interested in the Switch Zelda games.
We got Mario Kart 8 and Let's Go Pikachu for my son (the Switch is for his birthday). I might try Let's Go Pikachu but don't really care for Mario Kart. I'm keeping an eye on the Ori games too.
What I'm mainly interested in is Switch games that you can't play on the PS5 (which is my main platform). I don't really do mobile gaming so the Switch will pretty much be a home console for all intents and purposes, so I'm also not really affected by games that are "good for Switch mobility" like Hades (as an example--I already own that on PS5).
Nobody mentioning the Xenoblade series? If you like long JRPGs with 100s of hours of gameplay look at Xenoblade Chronicles 2 and 3!!! Recommend starting with the second one, but it's not neccesary to play them back to back