Looking over some of the new "Fan Collective" Star Trek boxed sets--in which ST fans pick episodes to go in themed sets--I was struck by a few things about the Star Trek phenomenon that I had already known but hadn't really thought of for a while. I noticed that, between the Alternate Realities, Time Travel and Borg sets, you can get pretty much all of the episodes of Star Trek: Voyager that are worth watching. I'm particularly gratified to see "Before and After" included in the former set--it was the rare Voyager episode that managed to be both compelling storytelling and strong character-wise, and the reverse-chronology storytelling (but linear from the character's POV) was pretty mind-bending (and it was several years before Memento came out).
In any event, the Voyager selection in these sets is fairly strong. Voyager was generally a fairly weak show that spent too much time with uninteresting characters without making a legitimate attempt to develop them. Aside from Seven and The Doctor, none of the show's characters were engaging, and few were well-written. And this was always the case. Even the first two seasons--probably the show's best--were weak overall, but they showed quite a bit of promise. The promise of Voyager was having a Star Trek show that coupled the challenging and difficult moral and political quandries of the superior Star Trek: Deep Space Nine with the good ol' formula of tearing around space and exploring new worlds. The idea of the "two different crews working together" had juice, and that the characters were weak made little difference--they'd get better, presumably, as the show went on. Actually, they got much worse: the crews effectively merged by the end of Season 1, bad boy Tom Paris swiftly became a trusted senior officer, and Captain Janeway went from half-mommy, half-taskmaster into the worst sort of hypocrite, swaying from strict inhibitions at sharing technology to doing so with a shrug if it were called for. The show had its moments, and while there are a handful or so of them that aren't on these DVDs you get pretty much what you need from the show on these sets.
As pertains to Deep Space Nine, though, the situation is reversed. Virtually all the episodes contained on the three aforementioned sets hardly represent Nine's best. Quite the opposite, in fact: the "Alternate Realities" set contains all mirror universe episodes, and the "Time Travel" set contains "Little Green Men" and "Trials and Tribble-ations", all of which are good shows but that don't exactly tell the story of Deep Space Nine. It merely proves that DS9 fans are not typical Trekkers, and vice versa.
It is true that DS9 did not exactly OD on time travel stuff as much as, say, Voyager did. DS9 generally eschewed the usual Star Trek trappings in favor of human drama, and the crew did little time travel during its run, but it usually had the best time travel episodes of all the Star Trek shows because DS9, unlike the others, usually didn't bother with all the cerebral wrinkles of time travel and continuity and all the rest. DS9's shows focused more on the emotional effects of time travel. The best time travel show the series ever produced (and probably one of the finest DS9s ever) was "Children of Time", in which the crew meets their ancestors on a distant planet where the crew crashed 200 years earlier, due to a time travel mishap. The scientific implications would, in all the other Star Treks, take center stage: how do we continue the timeline? On this show, though, such things are a background subplot, and the stakes are quickly resolved: either the crew has to recreate the accident or their descendants die. Characteristically for Deep Space Nine, the fix that solves everything (that other ST shows would come up with) is quickly discarded as impossible. Instead, the show forces its characters to confront difficult questions and work through them. And what follows is not one for the annals of heroism, but a gut-wrenching choice that clearly bothers everyone. And there is, of course, the deepening of the love story between Odo and Kira, which is handled as sensitively and winningly (and melancholically) as possible.
And this is how DS9 differed from the rest of the Star Trek universe. I have great affection for the other ST shows, but Deep Space Nine is the only one that ascended above mere entertainment coupled with the occasional paean to liberal conscience. It seriously grappled with the difficulties of a progressive vision of the world, but in a far more incisive and hard-edged fashion before ultimately concluding that such a vision is possible, but you have to work like hell to achieve it, and then you have to work like hell to maintain it. A lot of people said that the show was a betrayal of Gene Roddenberry's optimistic view of humanity, but I disagree. It was a fulfillment of said vision, only with a bit of the details of how to achieve it fleshed out. DS9 presents the most compelling case for Roddenberry's ideas, since it tries to advance a more sophisticated argument on their behalf that seeks to give shape to form.
This might be why Deep Space Nine was ultimately so polarizing: it was the most forthrightly liberal of all the Star Trek shows, the original series included. But it also had a few "fun" episodes, from time to time, and those episodes have unsurprisingly become the favorites of the general ST fandom who weren't quite as interested in the sophistication of Deep Space Nine. I actually don't mind this too much--hey, they're good shows, after all!--but they do give a somewhat distorted view of one of the best TV shows of the 1990s.
(I am aware that the "Captain's Log" set does, in fact, include some of the more biting episodes of DS9's run. From what I understand, some of these episodes were chosen by the captains themselves, so my point still stands.)