Yes, all the series have interesting qualities. The original series has two great seasons and one patchy one. Within a 1960s action adventure format, it often managed to be quite profound. Star Trek was most interesting in that it was a voyage not just through space, but through genres. The Enterprise was a vehicle to get the characters to a location, then isolate them. It had aspects of an anthology series akin to The Twilight Zone. One week it would be a western, another week a Cold War submarine thriller, another week a trip to a Nazi-like state, then a courtroom thriller. There was a lot less worldbuilding in terms of the universe of Star Trek - the Federation, Starfleet and the likes developed slowly - often with contradictory names - until they settled in final versions. The classic Klingon ship design didn't show up until season three.
TAS is a 'bridging show', with the ship moving in the direction of the TMP version, and managing to tell some intriguing stories in the context of a Saturday morning children's cartoon series. The tragedy is that TAS was 'decanonised' for a long time for no reason other than some legal issues. I have no problem with TAS being in the canon, because...
... in the novelisation of TMP (now
that's an interesting book that every Trek fan should read!) written by Gene Roddenberry himself, Kirk's introduction informs us that the original series and TAS were 'in-universe', often fanciful, romanticised retellings of the adventures of the Enterprise and this book purports to give s definitive, accurate retelling of the events of the Vejur incursion. It was a pretty bold thing to do, but if you take the book at its word, it allows all TV and cinematic Star Trek to be treated as an in-universe, fictionalised anthology series. It's why the radically different approaches to the universe between TMP and TWOK-TUC can be accommodated.
The Berman era of Star Trek is most noticeable for how ship-bound it was. Many episodes could fall into a 'bottle episode' category and, once Michael Piller arrived, it kind of became a series about how an individual each week copes with life on a giant starship on a 20-year mission. Gene Roddenberry, when he founded TNG, stated his approach was 'revisionist', so he was willing to contradict past continuity. If you're a fan, probably the best thing to do is treat each series as a sort of 'universe in a bottle' and that there's a 'definitive' Star Trek universe out there that we've never seen nor read about (it all gets a bit Kantian if you go too far in that direction!!
)
I haven't liked anything post-2005, except Picard Season Three and I'm not one of those people who can keep watching something if I don't like it anymore. But treating the various series as an in-universe entertainment means I can ignore anything I dislike. I'm still not thrilled about Discovery and Strange New Worlds existing. Picard Season Three ought to have been the first season of new Trek in 2017, followed by new series set post-TNG.