The one I want the most is Skyward Sword HD, but I'd also really like a 2D Mario that's not NSMB, even better if it's hand-drawn.
Other games I'd like on the Switch:
From Nintendo: Luigi's Mansion, Mother 3, Wii Sports Resort sequel, new 3D Donkey Kong, Mario and Luigi game w/ cellshaded or hand-drawn 3D graphics, Pokémon Platinum remake (I wish), StarTropics reboot as a linear adventure/puzzle-focused game (AKA what Zelda used to be), Murasame Castle reboot, etc. It's about time Kirby went 3D as well.
From third-parties/indies: A Hat in Time port (The devs recently got a Switch devkit, so it's just a matter of time imo), Psychonauts 2, The Talos Principle 2, Bayonetta 3, Crash Bandicoot N.Sane Trilogy (If timed exclusive), a late Okami HD port, Bully port, Beyond Good and Evil HD port.