You made an apt analogy with presidential rankings, Vito: both depend on the criteria the ranker selects for "greatness" or "best," etc. Not easy for presidents, lots harder for Mafia Dons.
My criteria for most effective Dons would include building and expanding business, avoiding limelight, spending little or no time in prison, and dying peacefully. I certainly agree with all the choices made by you and the other posters so far, as well as Lilo's choices for the worst. And I'd include Luciano, even though he served 10 years in prison and was exiled, because he was the first modern Don: willing to include non-Sicilians and even non-Italians in the councils of power; farsighted in forming the Commission, and brilliant for not appointing himself capo di tutti capi. And, even though he wasn't a Mafia guy per se, and spent more than 10 years in prison and was a public loudmouth, I'd include Capone, because he pioneered relatively sophisticated rackets (business and labor "associations" among others) that set the Outfit on its feet after Prohibition was repealed; and because of his political influence.