when measuring athleticism, you should look at how those athletic skills can be used across all sports. the more the more athletic, the less the less athletic, ex: the ability to jump high is needed in basketball and football (WR) whereas a golfers aren't seen as very athletic because the skills in golf doesn't translate well in other sports.
so the most logical way to see which sport has the most athletic players is to see which sport has the most players that can also play another sport at a relatively high level right?
ESPN had an article awhile back that said MLB had the most multi-sport athletes. i don't know who has more between NBA and NFL but there are well known ones in both leagues like iverson, lebron, nate robinson, antonio gates, tony gonzalez, etc