Stargate: For the time, it did the Trek format incredibly well if not better. First season was rough, but oddly found its feet when SciFi took over (weird, right?) Good characters, great villains, fantastic arcs. The show “ends” multiple times, with the last few seasons being less than fan favorites. That said, if you love the characters by the end you may find yourself putting up with late season plot devices. Atlantis is good too, but shorter with slightly less compelling plot hooks. The short-lived SGU sequel/spinoff is has this man-v-man flavor not unlike DSC season 1, but doesn’t stand on its own lore-wise.
Babylon 5: The even more grounded DS9. But like the oft-compared Trek series, the production values are a 1990’s time-capsule, which (today) has a kind of charm to it. The story arcs center around diplomacy, subterfuge, spycraft, and interstellar war, all told in a universe that is delightfully consistent and charts its own territory. Characters play off each other incredibly well once the series gets going.
Galactica: I’m going to assume you mean the reboot*. This is a gripping serial epic with very few filler and bottle episodes. Characters grow and evolve, allegiances change, motivations shift, ethics are challenged, and whole personalities get re-written. You can slap “space opera” on the box and be correct, but you can’t describe more than two character arcs without filling your mouth with crazy nonsense. Yet somehow, it all works brilliantly and draws you in over and over again. It stands apart from the source material, but has lots of nods and references to the original so that the old farts in the audience are enthused.
(* The original BSG is a hot mess of amazing-for-the-time effects, cool characters, great concepts, and bad studio interference. Best enjoyed using mind-altering substances because that’s clearly what the writers were doing)