First, assume that every living male on the planet would like to be a professional athlete, with desire increasing in proportion to the sport's popularity ie money/sex.
Two, determine the average height/weight/strength required to play a respective sport.
Three, calculate the total pool of talent available within the respective segments competing to gain entrance. One's individual odds of 'making it' are proportional to the total number of competitors.
Results:
1. Soccer
2. Baseball
3. Ice Hockey
Now, for anyone that is going to reply that soccer, er, sucks, yeah, I agree - I just don't find it that interesting. BUT, the most valuable sports franchise is Manchester United, and some of the highest salaries are paid to soccer players.
Given the fact that you can be 5'6" and 140 lbs to play, the world-wide potential pool of athletes is in the billions. So, the draw is there - those that are stars are super-natural athletes.
Baseball is so obviously comprised of the best US athletes it's essentially laughable to even debate the point. Like soccer, but less so, one can be 5'9" and 160 lbs and still be competitive. How many males are this size? Oh, maybe 70% out of say a pool of 1 billion (that has an interest in baseball).
Regarding basketball: If you are 6'6" (small for the NBA), you might have a 1:100 (or less) chance of having played some college and maybe even tried-out for a pro team simply for being that TALL. Now, how many people out of the general population are that height? Try practically nil. It is so height delimited that it defies consideration.
Football: again, a freak of nature sport. If you see someone who is 6'4"/240 lbs on the street, you can easily assume that they have played football at some point. Even clods at that size are tried-out by high-school coaches.
Hockey would be higher on the list if it appealed to a greater range of the population. But, even withing its narrow sphere, the avg size requirements compared to the speed, endurance, agility, eye/hand, etc all make it a much more demanding sport than many others ie you have to be a great athlete to be a 'player' (yeah, there are thugs, but that's the sideshow aspect).