Star Trek took us to the brink of interplanetary travel, going off the air just months before the July 20, 1969 moon landing. Star Wars would not premier for 8 years. During this time American only had one real heir to the SF throne, Space: 1999. It is definitely a heir to Star Trek, even sharing the same executive producer that Star Trek had in its third season, Fred Freiberger. Another tie to Star Trek was that both Leonard Nimoy and Martin Landau both worked on Mission: Impossible.
Space: 1999 lasted for two season, each with a different feel and some cast changes. The first season is far more cerebral, with very metaphysical stories. The second season is more action oriented with a lot more violence. Most of the cast remained the same, but several characters left to be replaced with new ones, most notably the science officer. In season one we have an older, reliable and cautious man. In the second, we have a bright, intelligent, shape changing, alien woman.
The stories are very good for the most part, but it is hard to compare this series with the great science fiction series like the Star Trek franchise, Babylon 5, Firefly, etc. It is definitely a product of its time. Nothing wrong with that. There was a lot of good entertainment in those years and Space: 1999 is among them.
I won't do a rundown of every episode. That is best left for my favorites. I enjoyed watching Space: 1999, but it did not become a favorite. It is good, but not quite up to my standards. I found it a bit lacking in several areas, mainly the types of stories they told. While at the same time the acting was stellar and the special effects were outstanding. While the character of the stories changed from the first season to the second, there is a uniquely Space: 1999 character to all the stories. I'd it is this character that is unique that doesn't really appeal to me. Just not my type of series. But has I been an SF fan when this series was on, I would certainly have watched it and enjoyed it. A very worthy fill in between Star Trek and Star Wars.
Being a fan of Star Trek, Doctor Who, and Star Wars, it was a lot of fun to watch this series. It was filmed in England for broadcast in the US. It was intended to be a British SF show, but the two principle characters were cast with American actors (Martin Landau and Barbara Bain). It had a nice mix of American and British influences and is definitely the jewel in the American TV SF crown of those days. This mixture ended up creating interesting parallels with Star Trek and Star Wars. You can see how Star Trek influence Space: 1999 and you can see how Space: 1999 influenced Star Wars. Oh, not in the sense of story or setting, but in the design aesthetic. The Moonbase Alpha sets feel like they could be a redress of some rebel outpost set. They all feel connected, like part of the same family. In many ways they are.
And the actors just add to that. I didn't take note of any major Star Trek guest star, but the number of people who appeared in Space: 1999 and either Star Wars or Doctor Who (or both) is amazing. Brian Blessed is a case in point. He appeared first in Space: 1999, then later in Doctor Who, and finally in Star Wars Episode 1. Red leader and gold leader both appeared toward the end of the second season.
I mark Space: 1999 as a pivotal classic of 70's science fiction. It filled in a gap, advanced ideas and technology, and is enjoyable and entertaining. A definite must watch if you haven't seen it. Even if you don't find it to be one of your favorites, it is good and a valuable use of your time.