PAGf If MEDIA MONITOR By STEVE K. WALZ-TELEVISION WRITER Is Cannell the "Greatest American" producer? New York--During the past few months, I've noted that ABC's program ming executives have had a tough time keeping the network competitive in the all-important prime-time stakes. Although many reasons can be offered for the network's mediocre perfor mance, I, for one, feel that the prime- time strategists have been trigger happy in cancelling such critically acclaimed shows like "Ten Speed and Brown Shoe." The producer of the series, Stephen Cannell, is recognized by his peers as one of the truly gifted writer/producers in Hollywood. Cancellation is an inevitability in the TV series business, but Cannell, despite his reputation, has been the victim of hasty programming decisions for the past three years At Universal, Stephen helped mold "The Rockford Files" and "Baretta" into solid hits back in the early 70s. He was subsequently rewarded with the opportunity, as executive pro ducer, to mastermind the success of a new NBC series called "Black Sheep Squadron" starring Robert Conrad Slated up against ABC's "Happy Days," "Laverne and Shirley" and "Charlie's Angels" when they were in the 'Top Ten' (1977-78), "Black Sheep" did fairly well. Vet, Cannell was shocked to learn that NBC had decided to pink slip the pro gram "I had all of these figures that I showed to the network executives that indicated that 'Black Sheep' was building a good size audience, but it didn't help. 'Black Sheep' was a cancel led hit," Stephen maintained New beginning Restless from his long stmt as a Universal producer, Cannell came down from the mountaintop (geographically speaking) to launch his own production company, ala Spelling-Goldberg ABC quickly forged an agreement with the versatile producer to develop prime-time shows for their schedule. "Ten Speed and Brown Shoe" represented Can- nell's first, but ill-fated, effort for ABC. Surprisingly, Stephen had plenty of nice things to say about his present employers "ABC had made the most pervasive deal to get me They are a very young group who aren't stubborn They have good ideas, are supportive and are fun to work with The most important thing to me were the people It doesn't make a difference how much money your getting if the people aren't good I'm in the second year of my two year deal with the network, and I have no burning desire to leave. I didn't agree with their decision on 'Ten Speed,' but perhaps I made some mistakes too," Cannell modestly offered Part of Stephen's overall optimism stems from his latest prime-time venture "The Greatest American Hero," starring William Katt, Robert Culp and Connie Sellecca. Like a proud father nurturing his new-born child, Cannell boasted. "It's another departure type show. It's the story of an ordinary teacher, Ralph Hmkley, who has a close encounter with a UFO and is offered a suit with super powers to fight evil Unfortunately he loses the instructions on how to use the suit, and he has terrible problems flying in it He doesn't want to use the suit because it alsq messes up his life I'm taking the 'Superman' genre and putting the reality in it. Ralph Hmkley is you or me. William Katt is bright and attractive as Hinkley He's heroic in that this is a responsibility he must undertake. Katt is also very sexy, but he isn't a classic matinee idol. I didn't want plastic pretty " Like "Ten Speed and Brown Shoe," most of the nation's critics have found the show refreshing But the viewing public and the ABC execs will once again decide if "The Greatest American Hero" flys or dies Nevertheless, Cannell can proudly proclaim that he has lured the likes of Robert Conrad and Robert Culp out of semi-retirement for his pro jects His secret7 "I want my actors to be my partners I don't want to fight with them--I want them to help me." Cannell added, noting that Culp will help write and direct an episode or two in the com- Connie Sellecca, William Katt and Robert Culp comprise the cast of Stephen CanneH's new series, "The Greatest American Hero."