The original series was my favorite. I am still so sad Leonard Nimoy passed away. He is the voice of the Mugar Omni theater in Boston and was a guest on two of my favorite shows, The Simpsons and Futurama. I love sci-fi and Star Trek and the X-files were the first sci-fi shows I remember watching as a kid.
Love the original Star Trek, and in looking for other TV sci-fi from that era I discovered the German series "Raumpatrouille" launched in the same year http://www.imdb.com/title/tt0061289/ . It only lasted seven episodes (sadly), but they are all on the Tube with English subtitles starting with episode 1 https://www.youtube.com/watch?v=vJI4J92Btis -- highlights include futuristic "dancing" in their undersea base at the 10 minute mark, and the launching of their spaceship Orion from said base starting at 15:50 with a countdown that sounds like it inspired Kraftwerk's "The Voice of Energy". It's even lower budgeted than Star Trek with hilariously bad animations. But the actors buy in making some pretty silly scripts good sci-fi fun.