Haven't played much on Switch since getting it for Christmas. I've focused mostly on Zelda and Mario Odyssey. I also have downloaded a few games that are reminiscent of older games (or they actually are). From what I've played I can recommend:
1. Zelda: Breath of the Wild - This is the best 3D Zelda game, hands down. This is the game you should play.
2. Mighty Gunvolt Burst - Just picked this up last night. Very reminiscent of 8-bit Mega Man games. Only played a few levels, but I can tell this is a very fun game if you like Mega Man.
3. Mario Kart 8 - I only have this on Wii U, but for me it's the best MK there is, so I'm sure it's great on Switch.
4. Vs. Super Mario Bros. - An arcade game from the '80s that is almost identical to the original SMB. Almost. If you like SMB, you'll like this version. It's got some enough twists to keep it interesting.
5. Super Mario Odyssey - Fun game, but not much else. I got to the end fairly quickly. Not enough content before endgame, for me. But still fun. If you like the older 3D Marios, pick it up, but don't expect it to be the best, because it's not.
6. Blaster Master Zero - Basically a reimagining of the old NES game. Fun, but fairly easy given the original is almost insanely hard towards the final levels. If you like platformers, I'd recommend.
I'm looking forward to picking up Azure Striker Gunvolt 1&2, and Xenoblade Chronicles 2. I've heard good things.