Your right some of the good heavys wouldnt have the right body type to be successfull in all sports but I bet in basketball and NFL there are athletes who are different to the norm, its the same in all sports.

Mike Tyson is the prime example in boxing, normally if you saw a short bodybuilder, you wouldnt automaticly think "heres the guy to beat a whole divison up and become a great"
Some people excell because they have a burning desire, regardless of how they are built.

Also, if boxing were more popular, more people would participate and so would their friends and so on, the law of percentages would dictate that America having such a large population, they are bound to produce more talented fighters.

It should be brought back in to schools, boxing more than any other sport teaches discipline and respect, in a team sport where the burden doesnt soley rely on an individual, they can boast and brag about their team, whereas in boxing, you learn that disrespecting earns you an angry opponent in a sport where the aim is to hurt and render someone uncounscious.