What determines a sport to an individual is one of those gray areas.
Some examples of nonsports would be poker, chess, checkers, and autoracing.
With poker, chess, and checkers these activitiesare mental. In poker, do you have the best hand or can you out bluff your opponent. Checkers and Chess are both mental by trying to out maneuver your opponent.
In autoracing a driver can sometime determine the outcome if certain incidents occur to give him an advantage. But if all things stay equal it is the car that determines who wins. The money the team has for the best equipment and engineers usually determines which cars finish up front at the end of the race.
Is horse racing be a sport? It is the horse who is performing, the jockey really has little to do with the outcome. The horse either has it or it doesn't or the horse could be having a bad day.
Billiards would be sport because it puts one individual against another. Golf does the same even though it is a number of individuals against each other.
The Olympics determines what activities will become Olympic sports. Thus, many legitimate sports are left out of the Olympics.
A sport can be individual vs individual or team against team.
Everyone will have to determine what is a sport to them and the debate will go on.