I'm working on a thesis that the Fantastic Four was pretty darned important back in the day, and it struck me that three very similar juggernauts began at around the same time. All were sci-fi universes with a distinctive and unusual upbeat message, and all are still valuable franchises today:
1961: the Fantastic Four, leading to the MU. High concept, according to Stan: "If I were a superhero I would..." - none of that silly secret identity and capes nonsense, they live in New York and do Great Things, making the world a better place. All very inspirational and "excelsior." They spawned the biggest narrative universe the world has ever known.
1962 (aired in 1963): Dr Who. Began as an educational series, soon became a message about how optimism and non-violence can beat anything. By some measures the most successful sci-fi series ever.
1964 (finally saw production in 1966): Star Trek. Planned as a series of morality tales, in a future where mankind has pretty much got it right. A commercial and cultural phenomenon.
Can you think of any other franchises that are as upbeat and successful? I am not sure that even Star Wars counts, as it doesn't have the longevity (only 3 good movies), or the upbeat message (it's all warfare and aristocracy). Are these three a unique triumvirate?