I think you can pick out any of the major players that dominated their game and are considered the greatest. Gretsky, Payton, Ruth, Maradona, Bradman etc...
I'd have to give it to Michael Jordan though. Not only was he far and away the best basketball player of his generation, he also played professional baseball for the Chicago White Sox. OK, it wasn't at major league level, I think he played AA or something. But that still gives him the edge for me.