I have several sports I do like a lot.
Mario Tennis is probably my favorite of the recurring sports, probably the one I play the most. I was really disappointed by the recent output from Nintendo being Mario Sports Superstars, Mario Tennis Ultra Trash, and Mario Penny Asses because they offered superior core gameplay than the rather sluggish and spammy Mario Power Tennis or the awkward "I keep getting out... why" from Mario Tennis 64. It's the sport most easily accessible: you just smack a ball and mash the A button, but there's a bit of an intricacy where ball elevation and racket placement is important, and you really need to learn the difference between a topspin, a slice, and a flat, and know how to do lob shots and drop shots as the back of your hand.
Mario Power Tennis also offers the wacky cutscenes that everyone loves (or hates if you're a dual Luigi fan/Mario hater)
I miss item battle from Mario Power Tennis where you not only smack the ball around but you can grab item boxes by hitting them with the ball and toss items at people, Mario Kart-style, and I keep wondering how the hell they keep failing to return a mode that helps define Mario's sport as, well, Mario's sport.
Strikers I enjoyed but it's mainly one game, Mario Strikers Charged, and the voice acting of the previous game. There's not many games to it and I'm kinda dying for a new one, but the single offering I really liked was something, well, I really liked. Was legitimately difficult too, tough as nails, not something you'd expect from a Mario game. Anyhow I love the weird amount of edge and sci-fi Strikers Charged has, and they don't take it seriously at all. The game has a lot of techniques involving chipping, though I mostly just stuffed my team full of agile goalie hoppers and Mario since I don't have the patience to pass the ball around). I don't mind Next Level Games churning out another Punch-Out, since that'll be excellent too if we had it for Switch, but my selfish priorities would be a new Mario Strikers.
I also liked the sports compilations a lot, just less so in Sports Superstars since their offerings, while full games, don't have much beyond the gameplay. Sports Superstars is horrifically lacking in the stages and options (seriously no team co-op in soccer???), which is a bummer because each sport is really a full sport and probably worth playing. Mario Sports Mix has a constantly pesky issue with its character roster on the other hand, but it isn't as severe as the stage roster, and Mario Sports Mix has sports on par with Sports Superstars AND it includes some wacky side mini-games that Mario Power Tennis has offered.
The other options are also worthy to think about such as DDR Mario Mix and its fantastic plot (however this game is inaccessible given the peripherals it requires on top of the inherently restrictive state of GCN games) and excellent music, Mario Baseball with its huge playable roster and the fun of baseball where every hit you make is a terrible fly ball, and Mario Golf which is just a really good golf game and hard to NOT recommend barring maybe Mario Golf World Tour (mostly for having a huge chunk of a mode where you don't even use Mario characters in favor of Miis) but Mario & Sonic are my least recommended set of games. They have a few worthy minigames to try out, but they're hard justifying such a steep price.
The sports games in general these days are just really lacking. I wish Mario could step in and fill that hole of the cruddy garbage Madden and FIFA has cratered with. The past few years have not been kind to sports games and Nintendo's in a really good spot to provide that since people want Mario Golf, Mario Strikers, Mario Baseball, but maybe those sports games are just an experimental blip on Mario's history. I don't want it to be that way, especially since Mario Pennis Arses sold pretty well but had a short-lived online scene, but what I want and what reality is doesn't align.