Most overrated:
Paul Castellano; I think he had the right things in mind pushing the mob to involve itself more in legitimate industries, but he wasn't streetwise enough and didn't earn the respect of the rank and file, I think it's clear he relied pretty much entirely on Gaggi and the Demeo crew to keep the rest of the family honest and once they were gone he was almost taken out at once. Also lots of - points for the relative carelessness with bugs and such.
Castellano wasn't the greatest boss. Aside from the fact that he was a greedy fuck and that he often was too busy banging his Colombian maid without any sense of tact, he took quite the hypocritical stance towards the people in his organization. Gotti and his crew were under siege because of their involvement in the drug trade, while Castellano turned a blind eye towards the Demeo crew's blatant forays into dope slanging. He also didn't seem to bother much with the Westies, who not only sold drugs, but jammed more of that stuff up their noses than they sold.
That being said, he did run a reasonably tight ship administration-wise. I also think his perceived "lack of street smarts" is a bit exaggerated. He ran extremely lucrative scams and generally speaking he wasn't a pushover either. He wouldn't hesitate twice of having you whacked when you posed too much of a problem. To the outside world he seemed to be a class act.
All in all, I think Gotti did far more damage to the Gambino's than Castellano would've done in the long run.
Most underrated:
Carmine Galante; Controversial pick maybe? Here's a guy who by most accounts had seriously low IQ(I doubt the accuracy a bit but yea), and managed to run or at least participate in serious international transaction and was savy enough to impose himself despite spending a decade or more in jail, adn even managed in a couple of years to impose Bonnano rackets in Montreal while establishing a bridgehead there for the family.
Personally I don't think Galante qualifies as "underrated". The only thing he had going for him - in New York - was his fearsome presence and his bond with the Sicilians. The Sicilians loved him, but the Americans couldn't stand him. And his bread and butter was in America, not in Sicily. The lack of respect for his ways of doing business in his own environment cost him in the long run.
