The Expanse looks promising as a "hard sci-fi", but the first season seemed to drag out without advancing the story that much. The show has a ton of characters, so none of them stand out.
RIP Dark Matter. It was brilliant.
Stargate Atlantis was the best of the 3 Stargate series. It was consistently good. Stargate SG-1 that preceded it was uneven, and a little rough in the first season, but it turned out to be a great series. Stargate Universe got off to a very weak start, but by the second (and last) season it was really wonderful.
Babylon 5 in the 1990's was science fiction on the cheap. They used workstation computers to generate their special effects to save money. The first season was not that great. But it had an extremely rich storyline. The show improved in the second season and it turned into a wonderful TV series.
Star Trek Enterprise was my favorite of all the Star Trek series.
As far as "space" shows go, I don't think anything beats Battlestar Galactica.
LOST is more fantasy than science fiction, although it had a few science fiction elements. It is mostly a drama series that blew everyone away at how great it is. It is also more complicated and harder to follow than most shows.