IT WAS MARIO PUZO’S bestseller “The Godfather” that immortalized that dubious assurance, “This is just business, not poisonal.” Yet if you believe what you read about the entertainment business these days, things more and more seem to be “poisonal,” not business.

Rarely is a major news story reported without direct reference to Rupert or Sumner, Michael or Edgar, Harvey or Barry. Indeed, not since the heyday of the studio system 60 years ago have a few ruling ubermavens so dominated the media landscape.

Ferocious as they were, it’s still hard to imagine Hollywood’s founding fathers holding forth as boldly as the men who run today’s multinational powerhouses. Not even cantankerous Harry Cohn, founder of Columbia, was as aggressively litigious as Sumner Redstone, who this week is back in the Delaware courts taking on Barry Diller over USA’s wrestling deal.

Similarly, it’s hard to imagine old Walt Disney leaving his drawing board to go to war with Time Warner on the issue of cable distribution of ABC TV shows, as did Michael Eisner a couple of weeks ago.

I was discussing these intergenerational comparisons the other day with a qualified observer named Bob Thomas, a genial 78-year-old who has crafted some 30 biographies about the moguls of old. As Hollywood correspondent for the Associated Press since World War II, Thomas knew virtually the entire cast of characters (his books are being reissued by New Millennium Press).

HE MAVENS OF THE ’30S AND ’40S, of course, had one key thing going for them. In their brief moment of glory, they exercised absolute control over their universe. If a David O. Selznick or Irving Thalberg didn’t like the way a movie turned out, he’d simply do it over. They were unencumbered by the demands of superstars or superagents and, as such, had final clout as well as final cut.

By today’s standards, their companies were vastly undercapitalized. They lived like feudal lords, but their fiefdoms were puny.

The Murdochs and Eisners of today have vast resources at their command, but complex constituencies to placate — investors, legislators, foreign partners, etc. Their level of sophistication in dealing with these power bases, to be sure, far exceeds that of their predecessors.

Rupert Murdoch’s need to conquer is reminiscent of Louis B. Mayer, but Mayer never had the fiscal know-how to implement his grand schemes. Selznick was habitually running out of money, even having to pass the hat to complete “Gone With the Wind.” Walt Disney, probably the most creative mind of his generation, ran his company like a corner drugstore.

It was not surprising, therefore, that the barons of yesteryear were utterly paralyzed by the threat of change — especially changes in technology. Television was dismissed as a pipedream. The mind boggles how these oligarchs would have responded to the Internet.

In part, their inability to adapt stemmed from their egomaniacal self-obsession. A man of astonishing grandiosity, Thalberg was so focused on increasing his autonomy and renegotiating his deal — a constantly ongoing process — that it’s amazing he had time to work on movies. Jack Warner was so consumed by money and power that he became “the clown prince” of Hollywood, not its ruling titan.

Selznick produced his classic at 37, then spent the remainder of his days trying to top himself, which turned out to be a futile exercise. His final effort was to remake “Gone With the Wind” as a Broadway musical; fortunately, he couldn’t raise the money.

Cohn was so persuaded that the escalating demands of “talent” would cost him his empire that he managed to alienate most of his stars and filmmakers. His deal with Stanley Kramer had a budgetary ceiling of $980,000, so when Kramer spent $2.4 million on “The Caine Mutiny,” he drove the brilliant filmmaker off the lot. The film, of course, was a hit.

IN THE END, HOLLYWOOD’S old barons became so paranoid about the changing economics of their industry that they self-destructed. Today’s mavens, by contrast, seem fiercely determined to sustain their reigns. Wildly opinionated though they may be, they also are proving to be shrewdly adaptive. They’re embracing new technology, not distancing themselves from it.

The old guys were tough, Bob Thomas reminds us. The new guys may prove to be even tougher.

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