I was thinking along these lines the other day. When I heard the announcers of the TdF saying that cyclists are the best athletes in the world. I think that's crazy. There are football, soccer and basketball players that I would consider far more "Athletic" than most riders.
What I think is interesting though is the aspect of the sport. Anyone can play a full basketball game a la the best in the NBA. I'm not saying any cyclist is gonna be as good as LeBron James or anything but they're capable of playing a whole game. Same for the conditioning aspects of football and some other sports. I don't think the top athletes in the NBA or NFL could ride 100 miles on a whim. Could some socer players? Probably. But not most.
Cycling is probably one of the hardest sports. I would say, on a recreational or professional level, its harder than most of the popular sports.