Maybe you could decide if a player is a superstar by the amount of All-Star games he has started. If a player is a lock to start the AS game on a yearly basis, he has reached a certain status: he's on a winning team, he's the leader of that team, he produces incredible stats, he's plays an exciting game, is loved by fans and a true ambassador of the game and the NBA.
There was a timespan in the early 2000's where every year the Western squad was represented by Shaq, TD, KG, Kobe and Kidd (or Payton/Nash). Maybe CWebb or Dirk were in there for a couple of years, but that starting line-up basically stayed the same. Those were superstars without question.
The East has/had a similar thing going on, first with AI//VC/TMac and now with Lebron/Wade/Carmelo.
Maybe you can only be called a superstar after multiple years of success, it's difficult to draw the line...