One of the greatest assets of Filmation during their existence was in their licensed properties, from Superman to He-Man. One of the more successful of these was Flash Gordon, which debuted on NBC in 1979, predating the live-action feature film by almost a full year. Hewley1972 uploaded the open to YouTube:
Regarded as one of the more faithful adaptations of Alex Raymond's fabled comic strip, Flash Gordon became the first Filmation series since their adaptation of Star Trek to last more than one season at NBC. Their track record otherwise was not that great, as most of the series they sold to NBC usually ended up cancelled after 1 season. Robert Ridgely (Tarzan, Lord of the Jungle) voiced Flash, while character actor Alan Oppenheimer (ex-Six Million Dollar Man) was cast as Ming the Merciless. Oppenheimer began a long association with Filmation with this series, and would remain a mainstay at the studio until it closed after the cancellation of Bravestarr in 1988. King Features owns the rights to the series, I do believe.
Flash would return, this time in a weekday series, as one of Marvel's Defenders of the Earth, which the comics giant would co-produce with King, through Hearst Entertainment, in the late 80's.