My sister and I must have loved Star Trek--more her than me, as I remember--because it was the only TV show our parents let us stay up to watch. I also remember my sister--and unusually, not myself--owning copies of Nimoy's Dot albums, which included (among other atrocities) the legendarily bad "The Ballad of Bilbo Baggins" (easy to find on YouTube) and the chart single "A Visit to a Sad Planet." Now, how an actor not known for his singing got a record contract? Well, it might have had something to do with Star Trek being filed by Desilu, which was owned by Paramount, which in turn also owned the Dot label (making one wonder how William Shatner wound up on Decca and Nichelle Nichols to Epic). Dot also signed Mission: Impossible's Greg Morris, who put out one album, and of course Leonard turned up on that show after ST was done.
Why we remember him fondly we can also thank ST's various writers for, but it took a good actor to take what could have been a freaky role and bring, well, humanity and (yes!) logic to him. The half-human, half-Vulcan also reminded us of our own mixed heritage, something lost amidst all the violence and meanness of the world. Spock was a unique character for television in that he had genuine depth, more going on than seen on the surface. A once-in-a-lifetime role that made him famous and typecast him in many ways, but perhaps that's because there was more Nimoy in Spock than the man cared to admit, that he really did create one of those fictional creatures whom, like Sherlock Holmes, King Arthur, and a few others, really sink in and tell us about a potential most of us never come close to reaching--for better and worse.
RIP.
ED