What if the NBA age limit was in place when LeBron, Kobe, KG, T-Mac, Amare, and others come into the League?

How good would LeBron, Kobe, KG, T-Mac, Amare, Dwight Howard, Monta Ellis, and Bynum be in college and what college would they have gone to. Would it have helped Kwame Brown, Eddy Curry, Gerald Green, and Telfair if they had to go to college at least for one season