You of course are referring to the bosses' personal picks. Your guess is as good as mine.. Different bosses different picks. I say "bosses" because I don't think there is one "highest ranked" boss across all families. Different families, different bosses. NYC alone has 5 bosses, so if you are looking for the highest rated boss, you will need to rank the families too. The Gambinos or Genovese families are the largest by count of made men.. But don't forget Chicago, another city with a rich mafia history!
But the real answer is these guys have money on both sides because they all get a cut of their bookmaking operations.