Disallowing The Expanse seems arbitrary. While the show is based on a series of novels and it did not tell the story of the last three books, the show itself ends with what felt like a satisfactory ending. Even though we were left with unanswered plot threads I am sure we can all think of some shows that were "complete" that suffer from the same problem.
1. Star Trek - I grew up with Star Trek, it's possibly in my DNA. There was a transporter accident, I shall not elaborate further. 2. Doctor Who - I do confess that the size of the canon might be why these two rank 1st and 2nd. While I haven't watched much of the classic pre-revival Who, I have sampled it. 3. Babylon 5 - If I were to say which three shows most influenced me as a kid growing up, it'd be ST:TNG, Babylon 5 and Buffy. This remains to me an iconic show. With flaws, to be clear, but still very rewatchable. 4. Andor - TBH, if we were looking at average quality of an episode, Andor should be the top one, but because it's only 2 seasons, it doesn't have the weight of canon of the other franchises. And I'm disinclined to throw all the Star Wars shows into a blender, when the rest were ... middling to okay. Andor deserves to stand apart. 5. Battlestar Galactica (reboot) - I don't think BSG stuck the landing, but I have different beef than most. I don't mind the revelation of the nature of Head Six or the Final Five or most of the character's fates. My beef is with
Lee's speech about abandoning technology and scattering across Earth. I dunno, I find it Luddite talk and an automatic death sentence to the people who have been living on spaceships for the past few years.
But regardless of the ending, it is still a solid show and worthy of being on my personal list.
Outside of the top 5 ... this is just honorable mentions, I can't quite order them
The Expanse
Farscape
Sense8
The X-Files
The Outer Limits (more the 90s reboot) and the Twilight Zone - these anthology shows kinda fit as a pair for me. Black Mirror would make it a trifecta if I would actually watch the rest of it.
Finally, 4 ineligible shows that I want to talk about that died too soon:
The Middleman - The whimsy of this show was endearing. But this was a show on the wrong network, which is a shame.
Dark Skies - Anyone remember this one? In all the rush of X-Files rip-offs, this one as a 60s period piece kinda stuck out for me. I've not revisited it, if I can even find it, but it's one that has stuck in my brain.
Earth 2 - Taking the "Wagon Train to the Stars" quite literally, this was a bunch of settlers on a new world. I don't know how it would play these days, I'd imagine using aliens as indigenous stand-ins would rightfully raise an eyebrow or two, and there simply isn't enough scenery for Tim Curry to chew for his short guest spot, but I really liked this show when it aired. This, however, ironically probably died when it should have, some of the plans for S2 were appalling.
Space: Above and Beyond - WW2 ... IN SPACE! Some fun bits, I'll admit I didn't care much for the lead pilot. This show managed a dialogue-less episode way before Buffy's "Hush".
Do limited series count? Here I am thinking of V, and its sequel V: The Final Battle. Shocking in its time and influental, I feel it/they should be on the list.