sheer pound for pound quantity+quality its hard to beat star trek. You could infinitely rewatch bits of TOS, TNG, DS9, Voyager, Strange New Worlds, and Lower Decks and basically never have enough time to watch anything else. None of the other shows comes even close on an hours level although Stargate is the closest.
The Expanse seasons 1-3 are amazing and up there but imo the story quality drops every season after that.
I'll have to revisit BSG, I have a feeling the final season will be a bit better now in retrospect but it does have that Lost vibe of things kinda falling apart story wise in the last season, and you can tell "they didn't have a plan" and didn't stick the landing. Should be interesting with the constant news of (another) reboot.
I do love Stargate and its one of the few that has a lot of comedic episodes along drama/action, and there is a massive quantity to it between SG1, Atlantis, and Universe. It is bizarre Amazon has been sitting on the IP for years now and done nothing substantive.