Humphrey Bogart and his “African Queen” co-star Katharine Hepburn led the American Film Institute’s list of the 50 greatest screen legends. (The legends had to begin their careers before 1950.) The roster was unveiled during a three-hour special Tuesday night on CBS. Cary Grant was No. 2 on the list of greatest male actors, followed in the Top Ten by James Stewart, Marlon Brando, Fred Astaire, Henry Fonda, Clark Gable, James Cagney, Spencer Tracy and Charlie Chaplin.