The number of great lefties in any specific sport should depend on how much of an advantage a lefty has against a righty, based on the specifics of the sport.
Golf is one extreme where there's essentially no advantage because you play against no one.
At the other extreme left-handed baseball hitters have a significant advantage against righty pitchers. This is because it's easier to see the ball early in the pitcher's release, and easier to see balls that break in rather than away. And even most lefties are right-eye dominant, meaning their dominant eye is in front of their body when they hit.
Look at this list. Even though lefties are 10% of the population, roughly 50% of the best hitters ever are lefties.
http://www.baseball-reference.com/leaders/WAR_bat_career.shtmlComing back to hoops, I think lefties have some advantages, but some disadvantages. For example, a lefty shooter is going against the defender's right hand, which is usually the natural hand for a righty in terms of blocks and steals.