It is not an exact sience, but there are 12 ratings divided over 5 stars. So it probably breaks down something like this:
Stars
1 announcer
1 bench warmer
1 or 2 role player
2 6th man
2 starter
3 star
3 allstar
3 or 4 perennial allstar
4 superstar
4 MVP
5 hall of famer
5 all-time great
Please don't hold it against me if something elso comes out of the draft, but this seems the most logical answer
Having in mind that only 20% of the players are generated as all-stars or better, I am not entirely sold on this chart, especially without any empirical evidence.
"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve."