My definition of a true superstar is quite high, and no I don't think most players who are being called superstars fit the bill. I today's NBA I would put only LeBron, Durant, and Davis up there. Maybe Curry too. And I never thought Grant Hill was superstar. He was damn good, but not a superstar.
Grant Hill was a superstar from 1995 - 2000 prior to going down with injuries. During that 5 year span, he was 1 of 3 guys who was named 1st or 2nd team All NBA all 5 years. The other two were Karl Malone and Gary Payton...both superstars.