I take a bit of a contrarian viewpoint on this.
I put these types of things into one of two buckets.
1 – New fans. I think most of the instances people will mention, a player may have drawn new attention to a sport, but those “new eyes” are less likely to last. This happens a lot at the collegiate level where spouses of fans start paying attention, fans of a school’s other sports start paying attention, etc. Typically, the effects are short-term while that player is playing and dissipates shortly after.
A smaller subset of this would be whole new fans to a sport. This is obviously the hardest to measure but I think you could point to several clear instances of it occurring at the different levels.
2 – Existing and casual fans. They are far more likely to have drawn attention from existing fans or casual fans that maintain or renew excitement and energy. I think most of the time, people that already pay attention to the sport tune in or pay attention, or sometimes renew/extend/maintain their attention.
I'd say those that had the biggest lasting impact would be Tiger Woods, Hollyfield, Tyson, Jordan, Bird, Magic, Curry, Sheryl Swoopes, and Lisa Leslie.
