I don't think there is more than 10% of the male population that could run a 5 minute mile.
First and foremost, you have to take into the consideration your own perspective of what a 5 minute mile is. Some would say fast, others would say slow, some would say, its in between. Obviously if you're a fast guy, a 5 min mile isn't anything to brag about, but then again, look at where you stand in relation to the rest of the runners on your team, then the rest of the runners in your conference, then the rest of the runners in the state.
I'm sure the bigger pool of athletes, the more you'll find that being a 5 minute miler is pushing you further and further to the faster side of the standard deviation.
Also, people keep talking about how if someone trained 100 miles a week and did workouts that they could obviously run a 5 minute mile, but you forget the simple fact that it takes talent to even train half as hard.
To even train at a specific level usually requires some amount of talent. It would be similiar to saying that if we all trained like El G, we could all run miles under 4 minutes, but the difference is, even many of our best athletes couldn't train as hard as el g.
Are there kids in other sports that could potentially run 5 minutes. Probably, but you also have to add in all the other kids from those sports that can't, and i'd be willing to bet that even though you'd get higher numbers of men who could run 5 minutes, you'd still be losing percentage points because most of those mens teamates couldn't do it, at best, they would have the same percentage of sub 5's as the cc and track team, once again, at BEST.
I'd say 10% at best, no more than that.