I like all the Star Trek series and watched them all. Every series had its ups and downs. My preference in order of favorite to least favorite only represents 'as a whole' and there are individual episodes and story arcs that exceed the order of favorites to one degree or another.
Star Trek -- TOS/TAS
Star Trek -- Phase2/New Voyages
Star Trek -- Next Generation
Star Trek -- Enterprise
Star Trek -- Voyager
Star Trek -- Deep Space Nine
If I were to break it down further, I'd say that TOS seasons 1 & 2 (and some of 3) were the very best Star Trek ever. But some of the TOS episodes are pretty silly and so are exceeded by other series' better episodes.
Phase 2 just plain rocks.
ST:TNG had a lot of quantity of episodes that were very good. They also had a large quantity of forgettable ones in my opinion and had a lot of political correctness that was hard to swallow, IMHO. The first two seasons were not very exceptional in my opinion and far too repetetive of TOS which handled the stories better. It felt like they were trying to remake TOS and doing it with cheesy "Dr. Who" style video keying FX. Some of it just looked a lot more fake than TOS scratchy film did. Not all of it, of course. But there were episodes where it had a definite look of being put together with a digital box and not with an optical printer which at the time had a far more realistic look. Technical aspects aside, I really didn't like the characters much until "The Best of Both Worlds" which turned that show around for me.
Enterprise for me, worked well for most of it, except I didn't like the Xindi arc a whole lot. It started off well, but it got pretty mundane pretty quickly. I liked the first season and the last season the best. The last season went a long way to correcting a lot of things to be the way we knew them to be. The only disappointment I had with the series is that they had to bring in the temporal war issue and that they missed the best opportunity of all... telling the tale of the Romulan War. Maybe they would have, had they not been cancelled so soon. But if they had done that, rather than the Xindi, it would have been far better, IMHO. But the reason this series gets higher marks than Voyager or DS9 overall, is that it felt more like TOS to me, overall.
Voyager was a pretty good concept that repeately fell short. It had some great stories and a lot of good characters. It fell short in that they always rebooted it whenever something disasterous befell ship and crew. Way too many time fixes. Not enough Maquis vs. Starfleet tension, not enough continuity of stories over the long haul. Having pitched for that series and seen their reasons for rejecting some of the ideas we presented, I felt they underestimated their audience or had very little faith in their viewership. They were more interested in filling the timeslot with irrelevance than thought-provoking material.
Deep Space Nine doesn't really deserve the bottom slot. It has some of the very best story arcs in the TNG era and some of those are highly elevated and highly prized in my mind. But I didn't really like the formula of the series as much and I didn't care a lot for the Bajoran culture. It just didn't do a lot for me. I did like Kira and I liked almost all the characters, I just didn't like the 'Goes Nowhere, Does Nothing' feel of a space station, overall. They did a good job of telliing stories for the most part, especially in the Dominion War. That puts it over the top of several of the other series' story arcs for me.
It should be noted that I would still score them all in the 95% or better category of like vs. dislike.
All the series were good IMHO.
Ken
