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?
When your friends brag about their successes (winning percentages), you should check the overall odds of their parlay - if it is very small then it is not surprising that they win often. Yes, and a high percentage of winnings does not mean that they are in the black. It's pretty easy to get a high percentage of winnings - bet on the favorite and you will win very often.