I would say that sports betting is both skill based and luck based. It depends on how much time you put into researching teams, players, coaches etc. You need to know the sport inside out in order for it to be successful. The more research you do before placing bets, the better chance of winning.
If betting is a skill it would have make many gamblers a millionaire today, and many gamblers would have like to be using any amount of money to gamble because they know they are going to win anytime they gamble.
I guess betting is a luck, what you are not expecting from your betting can come to you to be happy or sad at the moment, which is the reason gamblers should gamble wisely for them not to be addicted to gambling.