The only Star Trek show that holds up for me nowadays is Deep Space 9. It’s the only one that has even remotely realistic and compelling characters, with plotlines and story arcs that had weight and consequence to them. There were many problems with Voyager (such as the weekly reset button, which made no sense), but lets talk about the characters.
Voyager had so much potential to really humanize its cast, as the journey home could become increasingly desperate and resources increasingly scarce. Starfleet would become less of an overbearing presence, and sheer pragmatism would become ever more appealing. You could have all sorts of conflicts as characters examine what parts of their Federation identity need to be preserved, and what needs to be pushed aside in order to survive and adapt to their unique circumstances. Some would probably relish that, and some would resist. I realize that some episodes DID touch on those themes, but nothing ever lasted or changed. And that lack of growth and evolution (in the characters and their policies and actions) was incredibly disappointing - they were as dully Starfleety at the end as the beginning. It was just TNG in the Delta Quadrant.
DS9, on the other hand, had a fantastic supporting cast with antagonist characters holding series-long prominence (the Vorta dude, the female changeling, Kai Winn, Gul Dukat), and many characters with conflicting motivations who were often on the other side of Team Sisko (e.g. Garak, Quark and even Kira once in a while). Sisko himself was thrown into the Bajoran religion, in a bizarre but ultimately beneficial twist that was a nice source of tension for him.
DS9’s characters actually wanted things, and beyond the crisis of the week, it helped define them and make them memorable. Quark wanted to become the Ferengi Warren Buffet, but was only quasi-ruthless. He also had a running power dynamic arc between him and his brother. Odo wanted to understand what he was, and where he came from, as well as come to terms with what he felt about Kira. Kira wanted desperately for Bajor to be free and safe, and wanted to make sure no one screwed that up, be they Cardassian, Federation, or even other Bajorans. Bashir wanted a fly honey (i.e. Dax), and to exercise his mental genius (e.g. cracking Garak, figuring out Section 31, etc.). Sisko was trying to just stay afloat with all the shit happening around him, and not betray the Federation or Bajoran trust, as well as raise a son. Jake, while being one of the weakest characters, at least had a consistent coming of age what-the-hell-am-I-doing-with-myself thing going, as well as the journalism arc. Even a seemingly throwaway character like Nog had HIS coming-of-age plot and the Starfleet enlistment. Kai Winn and Gul Dukat had their constant scheming and power plays, and whenever they showed up, you could see them working towards their goals every time.
Shit, do you even remember what most of the characters in Voyager were striving for? The Doctor wanted to be a real boy, and this was, to Voyager’s credit, a consistent and evolving theme throughout the series. But Paris? Kim? Torres? Janeway? I literally can’t remember anything about their goals and desires other than what their job made them care about. Paris wanted to be accepted as non-fuck-up, I suppose? Chakotay wanted to get in touch with his Native Americanness… somehow? Belanna wanted to… uh, cure her PMS? Kim wanted to… grow a pair? Tuvok wanted to… perfect his constipation face?