Invariably, the team that wins the NCAA tournament has at least one NBA-caliber player on it.. usually more than one. In the NBA, every team has at least ONE "star".. that's the way it's set up.. the worst teams get high draft picks so they can draft (what they think are) the best players.
But to your point, sure it's a nice little story when George Mason/Butler make the Final Four but they're not winning it... even though Butler came close they have some NBA players on their team. And similarly in the NBA you can make a run without multiple great players, but you don't win the championship. The Bulls continually fell short until Pippen, Grant, and others started playing at a higher level. The Lakers won with Shaq, Kobe, and great role players.. when it was Kobe and a bunch of average guys, they barely made the playoffs or went out early. Cleveland had good teams with LeBron but when they played the upper level teams, you could immediately tell the difference in talent level.