I'm a latecomer to this thread. Well done
@Scepticalscribe for starting it.
I'd like to deal with a couple of things.
Firstly, I agree with
@Scepticalscribe that Patrick Stewart's portrayal of Picard was essential to the franchise's re-birth back in the 80s. He gave the character an authenticity that bolstered some of the weaker elements of the first few series, not least of which were the shiny uniforms the cast wore in Series 1. I am not a fan of Jonathan Frakes as an actor in ST, although I think he did a good job directing some of the later movies. I'm afraid I think he was also a weaker element of the show, especially in the earlier episodes.
Secondly, I think it took several series for each of the franchises to establish themselves and hit their stride. I agree (again) with
@Scepticalscribe and
@jdoll021 that TNG took 2 series to establish itself. But I think it really took off in series 3 and 4.
However IMO the other iterations took longer. For me, it was only in series 4 that DS9 and Voyager started to approach the standards set by TNG. In DS9, IIRC this was when the Defiant was introduced. A starship, so that the cast of DS9 could 'trek', and a new villain, the Jem Haddar (I apologise if I've misspelled that) so that they could have more 'dangerous' story arcs. In Voyager, it was the introduction of 7 of 9, and a slightly darker tone that helped take it's writing to another level.
I think it was
@jdoll021 who queried the ending of Voyager. It ended with them returning home, but with a lot of loose ends. IIRC, the network decided quite late in the series production not to make another one. The writers needed to decide how to end it, decided they should get home, but didn't have time or episodes to spare to deal with the loose ends. Not the writers fault, or a failing of the series, in my view.
Thirdly, Enterprise. This was cancelled after it's fourth series. I think it gets a raw deal when the various iterations are discussed. It was cancelled just as it was getting good, and IMO it was always the 4th, 5th, 6th series that set the standard we remember them by. IIRC, it was another disappointing network decision. It was regarded as expensive, and not as popular as DS9 or Voyager had been. This was also the TV era (late 90s, early 00s?) when 'reality' TV was very popular, and incredibly cheap to make. IIRC there was also a view that there wasn't a market for SF TV shows at that time. The network was clearly wrong about that, because as they cancelled it another company was investing thousands and thousands in Battlestar Galactica which was a smash hit, and brilliantly acted and written (I think Battlestar Galactica is the best SF TV series ever made. Sorry TNG and Firefly fans).
I grew to like Bakula as Archer, but he carried a lot of baggage from his time as the lead in Quantum Leap. He may have been better received with a longer break between franchises. IMO It's almost the opposite of the Patrick Stewart effect on TNG. I suspect that with another actor the iteration would have done better.
Lastly, on the movies versus the double-episodes debate, as I have said before, these are not fair comparisons. A movie has to be a self-contained story accessible to fans and newbies alike. Double or triple episode story arcs in a well established series don't have these constraints. The audience already knows the characters, and the universe. They understand each character's history and personality. Good writers and a good cast can get on with great story telling from start to finish, and in TNG, and the later series they did just that. I think one of the reasons many of the fans were disappointed with some of the movies was that the double-episode story arcs were so good. Looked at objectively, I do think there are good ST movies, not least of which is First Contact.