- The appeal of the films is inseparable from nostalgia
- The films don't distinguish themselves as art or in their technique
- The films often include laughable situations (indeed, this is true)
In any event, I think that when analyzing something along the lines of Star Trek, one can easily attribute the success of The Original Series to 1960s optimism about the future and romanticism about the space race. But what to make of the enduring popularity of the series? Clearly, the appeal cuts a little deeper if it's survived for such a long time. After all, there's not enough nostalgia for a new Space:1999 movie, and the reimagined Battlestar Galactica was a complete departure from its predecessor series, which really was most of the things that Ed and Jason impute to Star Trek.
My sense of things is that what appeals about the series is a certain sort of optimism about the future and its characters that few shows and films (and especially few sci-fi shows and films) actually possess. I think that accounts for a lot of its enduring success, especially in the 1990s, when Star Trek was a huge business. It is true that it no doubt helped to basically have a monopoly on televised science fiction during the 90s, and that a recognizable commercial brand was able to do things that wouldn't otherwise have been done at that point in time. Sure, part of the reason it succeeded was that it was there and it filled a niche, and that's why Star Trek: The Next Generation was as popular as it was, but that show not only gave us some plainly good heroes to root for, but often the bad guys weren't really all that bad, just misunderstood. Even the Borg, ultimately, were vulnerable (though doing that was something of a mistake, in my estimation).
I tend to think that The Next Generation is sort of a model of successful television. Truthfully, a lot of it is banal or even bad, but it often presented interesting stories and mysteries, and did a good job of balancing the humanism and idealism with the demands of a weekly show. While the show often featured incomprehensible technobabble it managed to present compelling and interesting mysteries, and though plot-driven it often did feel character-propelled. It more or less stayed true to the original series' ideas while moving more into a mainstream direction (in a good way), and the show even managed to be occasionally moving. Episodes like "The Inner Light" and the show's finale brought a hefty dose of earned emotional resonance.
I think that Star Trek: Deep Space Nine was definitely the franchise's high point. It did push the winning formula quite a bit: it was on a station instead of a ship, characters wouldn't always act out of the noblest, disinterested motives, and the show often fixated on the messy internal politics of a fairly small region of space rather than seeking out new life forms and new civilizations. A lot of fans then (and still now) dismiss it as boring, but this is usually a sign that the person in question watched a few early episodes and said forget it. There is no defending the early seasons of the show, though the first 2-3 seasons of all the Trek spinoffs are generally bad, no doubt having to do with the security of being able to spend a lot of time on exposition before actually having characters do something. Truth is, though, that during its last four seasons the show was consistently excellent. This happened to coincide with the arrival of TNG's Worf on the show, who added the show's missing element. The later seasons of DS9 brought a cold war that turned hot, characters having to make difficult moral decisions and sacrifices, and more than a few tough deaths. But it wasn't boring and the storytelling was fast, intense, and surprising. DS9 pushed the limits of Roddenberry's vision but didn't exceed them--in fact, the characters' actions validated the humanistic approach that the shows and films had always took, even if it sometimes took people a while to come around. And it dealt with the religion and poltics of Bajor in an often penetrating and insightful way. This is still pretty rare to see on television.
Now, admittedly, with Voyager there began to show signs of decay. The show displayed quite a bit of complacency and a lack of imagination. The new races we met weren't as cool as the old ones, plotlines felt familiar, plot devices like time travel were overused. There were certainly watchable Voyager episodes--even some good ones--but the show rarely went for broke and decided to play it safe, figuring that the Star Trek name would be enough to keep it afloat. This proved to be rather wrongheaded. I can't really speak to Enterprise, of which I've seen few episodes, though I suspect it failed because of the same familiar storylines and a lack of guiding vision. These things were also evident in some of the Next Generation-era movies: Generations was a logic-ignoring baton-changer that wasn't quite as epic or compelling as it needed to be. Insurrection didn't fare much better, and it more resembled The Voyage Home, only the humor was unintentional. And the less said about Nemesis, the better, though at least its heart was in the right place.
All in all, what has characterized Star Trek over the past few years has been a lack of real ambition to move the series forward--such as both TNG and DS9 had, in different ways--and a lack of understanding as to why people tune in to watch these shows in the first place. Optimism is appealing, but well-constructed stories are essential. With another Star Trek film coming out it will be interesting to see how J.J. Abrams decides to deal with these deficiencies. I predict that the film will be a success (nostalgia + lots of action will go a long way), and if it is successful enough we might well see another show: the Era of Obama seems well suited to Star Trek's message of gentle humanism and optimism. I will follow Star Trek's example and remain, for the moment, optimistic about the possibilities.