This is a never ending debate with no real answer.
I bowl 2 leagues, one is an individual "challenge pattern" league (60 to 70 bowlers depending on the year) and one is a THS league.
In the challenge league we use 5 patterns throughout the season with varying levels of difficulty, I would consider that to be a "sport", not only because of the patterns, but because of the level of competition and the fact it is a singles league.
The THS league to me is more entertainment, I try just as hard in both leagues but I'll have a few beers during this league and good or bad, I have the same amount of fun with my friends. I still want to win, but I don't stress or obsess over winning or losing.
It is whatever you want to make of it, in the same THS league, some take it as serious as I take my challenge league so to them, that league is a sport.