What is the difference between a "star" and a "superstar?" Is there a definition? Do we apply the Supreme Court, "know it when I see it" rule to such a standard?
Part of the issue—aside from how difficult basketball is to statistically quantify—is the conflation of celebrity and productivity. A hyper-efficient basketball player will often get celebrity, assuring him of "superstar" status. But there are other means to getting noticed in this manner.
Often, an incredibly fun to watch player gets bestowed with superstar status. Blake Griffin and Carmelo Anthony come to mind as good players who benefit from market status and entertainment value.
Rajon Rondo might be a perfect example of superstar form over function. In the regular season, Rajon's only 21st among point guards in John Hollinger's PER and his team struggles to make shots (27th in offensive rank, according to Basketball Reference).
There is a legitimate reason for regarding Rondo as a superstar, though. He has skills that few other players possess, and if he can improve that jump shot (shooting has tended to improve over the course of his career), then yes, Rondo should produce at an elite level. Superstardom is within the grasp of anyone who can do this:
Then we have All Time great players, who retain superstar names despite declining in talent. I'm thinking Kobe Bryant and Tim Duncan for this category. There is a lag time between when a player stops being himself and when the sporting public takes notice. Perhaps such a phenomenon moves faster in the Internet era ("Is Kobe done???"), but a lag still exists.
I have my own, arbitrary definition for superstardom: If you're one of the five best players, then a superstar you are. It's a weaselly way to determine it (I'm not coming up with an objective measure, just an objective measure of a subjective one), but it is the best I can do.
So here is my superstar list, according to my own rules: LeBron James, Kevin Durant, Dwyane Wade, Chris Paul, Dwight Howard. Too restrictive? Wrong names? What superstar standard would all of you choose?