The first ST series I saw was TNG, which prompted me to track down and watch the original series. I liked both, but they're still the only two I've seen. Whatever came next, was it Voyager? I couldn't get into, but I was moving away from Sci-Fi at that point and getting more into historical fiction (reading, not on tv). Since our discussions here this past couple years, I've realized how much I miss Sci-Fi and have been reading and watching more of it. Have both TOS and TNG saved in my instant queue on Netflix to watch again. Also have never seen any of the movies (I know, I know, BAD!), so want to watch them in the near future too, or maybe after I've watched the series' again.
.... I figured the writers like the big drawn out story lines because it is less work than coming up with new stories. However, the shows are better when they stick with one or two hour story lines and drop the long stuff. As an example, I really liked early XFiles shows that were one hour independent shows. I got turned off when it turned into one season long alien plot.
I agree MechAg. It frustrates me when I miss a couple episodes and it takes me a couple more episodes to make sense of what's going on. As a writer, I understand the need for both character development, series continuity, and keeping people hooked, to have a long storyline woven in. But like you, when that starts to take over every episode, I lose interest and move on to something else. (I lost interest in the X-Files at exactly that same point.) I like the episodes that can stand alone. If they're going to have a long complex story line, they better hit on key scenes to explain things at the opening.
But, again from a writer's standpoint, it's very difficult to create a "world" and people it with characters and NOT have it take on a life of it's own. Every story I've ever written goes on much longer than "the end" and has far more going on in the big picture than the reader actually sees because the imagination is limitless. This is also where prequels come from. Wherever a story begins on a page, the writer has to go back and imagine how the characters got to be right there at that exact time. Often this leads to entirely new stories and a "holy crap, I should have thought of this first!" moments.