maybe GOLF or football and in recent times cricket is also growing very faster by financially and popularity..
I think it's boxing or golf. OR either Football or Basketball. It doesn't matter as long as athletes gets to be payed with the right amount they deserve.
I am sure t has to be f1 , atleast when coming to the highest invested game plays or highest pay games , next comes the fifa , atleast to my knowledge , but , can't really be sure on that to be frank