I'm a pretty big sports fan so it's kind of hard to pick for me, especially between my favourites.
My three favourites are football, tennis and golf. I've been playing football (English football) pretty much ever since I could walk and I've been playing in teams since I was around 5. I stopped playing properly when I was 15 or so due to me developing asthma which was sort of heartbreaking in a way because I just couldn't run as fast as I used to be able to. I don't have asthma anymore (I kind of grew out of it), but not playing for two or so years really halted my progress. I still play causally from time to time playing for my college team and I still follow football like it's a religion, lol.
Then there's golf and tennis which weren't really drilled into me like football was. My family loves football and pretty much every boy in the family has played it or is involved in it. Golf and tennis was slightly different as they eventually grew on me. I think I started playing both back when I was around ten or eleven. They were just a different type of challenge that I could sink my teeth into. Golf, I would say, is mostly mental; you're battling with your mind throughout the entire round. And tennis is very, very competitive as it's more of a rivalry with your opponent, which I enjoy. They were a challenge to me, so many techniques to learn, so many new things to master and both are just incredibly enjoyable. I stopped playing tennis a while back but I've recently joined a new club and got back into the swing of things, literally. Golf I've always played (sometimes on and off for periods) but that's the sport which I feel I'm at my highest level.
So I can't really pick between them, they all have their advantages. Golf is very rewarding and mentally stimulating as well as relaxing when playing causally- you can just get away from reality for 3-4 hours and chill in the sun. Tennis is extremely competitive and physically demanding esp when you're playing someone good. While I love the team aspect of football plus it's the most enjoyable to watch and follow. I love all three is the short answer.