I think the dual purpose QBs might be the best overall athlete at times, think Mike Vick, and a few others of his ilk.
I was watching the Braves game last night and the announcers talked about the pitcher who played SS in college, and at some point asked to have a shot at pitching. They said he would not have been drafted as a SS.
Marquis Grissom pitched in college and was moved to the outfield at some point, good move for him. The pitchers I know pretty well are/were really good athletes, I suspect most college QBs are pretty good athletes overall, but the "best athlete" in a team might be a safety often as not. Wide receiver, MLB, RB ...