Interesting question.

Like others said the Italian-American mob today is far from what it was in the past,but I do believe that at its peak it was the strongest criminal organization that ever existed simply by virtue of being the strongest organization in the strongest country. Like NNY78 noted, it's one thing to have power in Columbia or Italy or post-communist Russia, and another to have it in America. As far as money goes, the cartels and modern day mafias make more money because of drugs, but that only goes so far. And most of it ends up being seized. But as far as power goes, no one will ever have the kind of power the mob had in America.
The Pablo Escobars and El Chapos and Schiavones make their billions and are on top for a decade or two, but they all end up dead or in prison and unable to spend. There are many like them, but only a few like Carlo Gambino or Tony Accardo or Gery Catena who kept their money, died as free men in their own beds, and more importantly, their power was their own, they weren't simply rich pawns for other (government)players.

As for what made the mob that way, I think it was a combination of two things:

- the clannish Italian/Sicillian culture that made them very cunning and Machiavellian and anti-authority and adept at expoloiting the system, more so than their Irish and Jewish contemporaries.
- a perfect storm set of circumstances that are unlikely to be replicated: prohibition, the rise of the labor unions, gambling being illegal, Hoover being a huge jerkoff etc.