Here's my recommendations, I'll add in my total play time for these games if you're interested in them
Splatoon 2- Great and fun shooter on its own right, decent single player, the meat of your experience will be in online multiplayer, I stopped playing recently because the mathmaking prevents me from having any fun because now that I'm level 50 it just teams me up with shitty players and losing aint fun obviously. This game gets a bunch of updates that add in new weapons and sometimes stages every now and then which is a nice incentive for coming back to the game. 285 hours
Puyo Puyo Tetris - Really great puzzle game, joining the competitive puyo community was the best decision I ever made I made so many friends and this game is really what I play most of the time now, it includes both puyo and tetris you can either just pick up puyo or tetris to play with or learn to master both, either way this game is tons of fun with great music, characters, and replayability. 110 hours
ARMS- Really really competitive game the meat of this will be online 1v1s mostly, updates usually come monthly that add in new content to this game, this month there were two updates so we got a character and two new stages this month which is pretty cool. Single player is barebones right now, maybe you should pick it up at a discounted price? 55 hours
Super Bomberman R - Literally the BEST couch multiplayer game on the switch in my opinion, this game is a "blast"; ))) lol this game is also gets frequent updates that adds new stages and characters theres a new one coming out that adds in 3 more new character and new stages and new modes so I'm excited for that. Single player is fun and doesn't overstay its welcome. Online mutiplayer is really fun and hectic too and the game really boasts a great amount of charm. Love the music, love the characters, love the stages, love the combat. 100 hours
BoTW - You probably already heard of how great this game was. I only spent about 85 hours on it though because the world feels really empty to me with little enemy variety and I wish there were actual dungeons like in the other LoZ but thats a whole other story so anywayyyysss Its still a beautiful looking open world game that plays wonderfully, you'll probably really enjoy it. 85 hours.
Mario Kart 8 Deluxe - Really fun mario kart game, great tracks, great visuals, great soundtrack, great online multiplayer. 30 hours(I already played the heck out of it on the wii u so youll probably spend longer time with it?)
Sonic Mania - Not a switch exclusive but its a really great sonic game. The controls are very fluid, the special stages are fun to play, the visuals are so beautiful and the music is so freaking good. 25 hours
Honorable Mentions:
VOEZ- not the best rhythm game out there, music variety is lacking even with a catalogue of 100+ songs theres really only like ~10 songs that are memorable, definitely a great value though because if you opted for the mobile version unlocking all the songs would cost an upwards of 100+ dollars and for the switch version you get to pay 20 dollars for all the songs and theres even free updates from time to time that add even more songs. 5 hours
Thumper - Great rhythm game, very different type of rhythm game, it has great visuals and a nice difficulty curve, great mechanics that allow for a wide variety of different methods for racking up your score. It gets really hard and the game gets really intense I've never felt a game quite like this one, it's beautiful. 15 hours
Snipperclips: fun co-op game but its way too short for 20 bucks (only 3 worlds)! the puzzles arent really that hard either but they do feel good completing them. theres going to be a DLC that adds in more worlds for 10 more bucks, and honestly the game was already too short that the update shouldve been free but ugh. 5 hours
