There's no point. People interested in those types of games won't buy Nintendo's sports games.

New sports games? Yes. With Mario? No.
Splatoon almost became a Mario game, but they chose to make it a new IP, if Nintendo makes sports games, I would rather take the new IP route, because the ''Nintendo only has Mario'' argument needs to stop (My opinion though).

EDIT: They could also make an improved version of Mario Sports Mix that could be released once per generation, and include all the separate Mario sports series in one game. 

I think they should make there own line of sports games but not Mario and not sports sims like EA does, instead I think they should be somewhat of a middle ground between those two styles.

Think of Ready 2 Rumble Boxing compared to EA Sports Fight Night series, it was somewhat realistic but more of a lighthearted approach, I think Nintendo should go more that route.

That would be cool, but we've got to remember that Midway were the king of that sort of game and look what happened to them.

THIS... THIS... THIS!!

I had this growing up and I loved it!! I was stupid to buy All Star Baseball 2000 the next season though... It was a solid baseball game, but it was considered REALLY stiff from Ken Griffey's Jr's Winning Run.

They also had Kobe Bryant in NBA courtside!! That game was HELLA FUN!! I used to come over and play that at my friends house... Good times!!

They could contact major sport stars if they wanted to. I am 110% if they contract Cristano Ronaldo to some deal for a Soccer game, they will sell MILLIONS, just on his name alone.... and the game can be completely average.

You might be on to something bro.

When the hell did Mario All Stars become a sports title?  lol

I kid I kid... but seriously it would be nice if Nintendo returned to having a quality stable of exclusive sports titles like they did back in the day... NBA Courtside and Ken Griffey Jr Baseball were both the top titles of their respective sports on Nintendo systems, and at one point they even had *gasp* 3rd party exclusive sports titles like NFL Quarterback Club '98 and '99 and Wayne Gretzky 3D hockey on N64, which again were among the top games in their respective sports for the time.

But sports games are, like, sooo Western bro.  And Nintendo doesn't like doing things for the benefit of its Western audience.

Neither of those really fit the "sports" role very neatly. Pokemon are too varied in size and behaviour to make into a neat sports game, and Zelda doesn't have enough notable characters to really flesh out a proper sports title.

On the other hand, some of their other franchises would work. Animal Crossing would be a great franchise for some team sports - you could have a Humans team, a Staff team (Isabelle, Nook, Brewster, Copper, etc), and then a variety of different Villager teams, each with some sort of theme (Cats&Dogs could be one, for instance). Alternatively, have each team with one Human, one Staff, and some Villagers, with the Human and Staff being the "main" characters as far as special skills go.

For something more along the lines of wrestling, etc, perhaps bring in both Punch Out and F-Zero.

That being said, I actually think Nintendo should be part-funding a variety of studios to develop games of a variety of types, and they could just have Nintendo IP cameos added along the way. They could partner with various publishers in creating these studios, with the goal being that the same studio could also work on games within the other publisher's franchises. For instance, if Nintendo made a sports studio with Sega, they could also work on Virtua Striker and Virtua Tennis (note: I'm not saying Sega would be the best partner for a sports studio). This would also have the benefit of improving ties between Nintendo and various third parties.

Mind you, I wouldn't have them form a studio with EA.

Mario is the centerpiece of a fleet of games that Nintendo makes. He's like Mickey Mouse.

The amount of facepalm....

Mario Tennis
Mario Golf
Mario Super Strikers
Mario Sports Mix

Every damn sport covered

Sure, why not? And not even Mario, just make cool generic sports games, no need for real teams or anything.