My favorite is Star Trek, TOS.
It wasn't just a show about the United Federation of Planets. It was a show that introduced controversial topics to get society to start thinking about it's unconscious biases.
Kirk and Uhura had the first televised Inter-racial kiss (Plato's Stepchildren). Chekhov was a very explicitly Russian and serving on the command bridge while the Cold war was at its peak in the nation. Racial biases were exposed by illustrating black/white skin color explicitly (Let that be your Last Battlefield). The Declaration of Independence was examined in terms of understanding meaning versus repeating words by rote (The Omega Glory) Many other issues were introduced in a fashion where they could be examined outside of the personal biases of the audience.
Gene Rodenberry wasn't just introducing a new Sci Fi universe, he was working to bring about social change as well. Plus, the interactions, humor and loyalty between Kirk, Spock and McCoy set the bar for every other series in the ST universe.