In what basically started as a hobby of mine, was to figure out what a championship squad needs. It helps to look at all the past champs, even past Finalists and see what were on those rosters and what led to that success. What kind of player a team needs to actually win a championship isn't by any means rocket science. The vast majority of champions are clearly top 5 players. But players between top 5-10 pop up and win ships here and there. What hardly ever happens is a team winning without a top 10 player.
For me a superstar comes down to their overall numbers, awards, and what they look like playing (the eye test). Their offensive numbers are generally key, having great defensive stats helps, but isn't required. I've come up with my own very subjective formula for figuring out a superstar.
As I've stated in other posts, much of it ends up in retrospect as you need time to review things. I may also add certain stats to it as well in the future to better flush it out.
I also try my best to limit superstars to 10 players in a particular season. Some seasons there are only 4, some there are 10 (like last year).
I have used PER in my rankings, and over the course of the last 50 years, generally a PER over 20.0+ is required. Today players are a lot more efficient than in the past, so I may be modifying my own rule on that. 20 years ago 22 players had a PER of 20.0 or higher, last season 42 did. Of the 10 I considered superstars in 2020-21, they all had a PER of 24 or higher.
Winning an MVP is pretty much automatically making one a superstar. I also consider MVP vote shares, but then it comes down to making All-NBA 1st/2nd teams.
The next thing I look for is consistency, which means doing one year of 25 ppg, 25 PER, All-NBA 1st, isn't enough to make one a superstar. I like to see two seasons in a row of doing that.
The last two things come down to a sort of eye test, aka can a player take over a game, score clutch baskets, or be known for making key stops. The other is leading your team successfully somewhere. Going to the first round isn't much of an accomplishment, dragging your team to the conference finals or beyond though? That is something noteworthy. Obviously teammates play a role in this one way or another, but we've seen a guy like Allen Iverson pretty much drag his team to the Finals, while a guy like Tracy McGrady never left the 1st round.
Obviously eras change things and then some adjustments are needed, there are always exceptions as well, but the gist of it stays the same.