In the shorthand of news coverage, law-enforcement officials said, the subtleties of who had really put the cases together and where important evidence originated often be lost.

Law-enforcement experts agreed that the enormous insider-trading investigation began with a tip to the Securities and Exchange Commission, not the United States Attorney's office. The S.E.C. developed much of the evidence and worked, as it usually does, with the prosecutor's office to exert the force of criminal sanctions.

The enforcement director of the commission, Gary G. Lynch, said of Mr. Giuliani: ''He certainly was involved in the decision-making process. But certainly there were other important players, as well.''

Mr. Giuliani receives high marks for personally winning the conviction of Mr. Friedman in the Parking Violations Bureau scandal. Often not noted, however, is that his office first received the case because a Federal informer in Chicago told investigators there that New York officials were taking payoffs. Work of Others

The foundation of Mr. Giuliani's reputation may have been the major cases against organized crime and a precedent-setting victory over the ruling ''commission'' of five Cosa Nostra families. But several of the major Mafia cases were already well along when Mr. Giuliani took over the prosecutor's office in 1983, said his predecessor, John S. Martin Jr. Many leads that became the well-known Pizza Connection case were being pursued by officials in Brooklyn when Mr. Giuliani took control of the investigation. ''I think it's fair to say that Rudy took what was there and developed it further,'' Mr. Martin said.

Even Mr. Giuliani's harshest critics said he often acknowledged the roles of others in important cases. But as his term went along and the press grew increasingly attracted to the ''superprosecutor'' image, Mr. Giuliani seemed to enjoy the limelight.

With Senator Alfonse M. D'Amato, Republican of New York, he went with drug agents to Washington Heights to demonstrate a drug purchase. Later, a widely distributed photograph showed the Senator and the prosecutor posing in disguises and dark glasses. Some said the escapade worked as an imaginative warning to the public about the increasing prevalence of drugs. Others dismissed it as a publicity stunt. Use of RICO Act