Although Doctor Who is my biggest love in televised Science Fiction, Star Trek is a close second. I watched it on TV when it first aired in the 1960s, and again in syndicated reruns. Now I own a few boxed sets of BluRays.
The Original Series (1966-1969)
I know watched this when it first aired. In 1966 I turned 15, and I had been reading science fiction and fantasy for some years already. And the series was sold into syndication after the initial airing, and proved very popular there, which certainly helped when the decision was made to make films and the follow-on series Star Trek: The Next Generation. But to do this analysis I purchased a boxed set of the complete Original Series on BluRay disks, and watched the shows in order along with my wife so that everything was fresh in my mind, and so that I had a perhaps more mature view of the stories.