I have a few friends who bet on basketball, mostly NBA, and they've an amazing track record of 55% winning parlays. I have probably 2 or 3% on football. They keep telling me that betting on basketball is easier but I still don't get why. Any clue? do you bet on that?
Best sports to bet on is the sports you understand so you can easily place your bet and you can execute your betting plans since you know the teams and you know every skills of the key player.
I do bet on NBA most of the time and I followed the league for some time now. If you do place your bet on a sports you are not familiar with, then you might just increasing the risk of losing money. The best sports will always depend on your standard as a gambler.