I recently finished watching all five seasons of Babylon 5 (plus the pilot "The Gathering" from the Movie Collection.)
Watching the entire thing, several episodes a night—once I watched all four on a DVD because I got so caught up—gives a sense of the entire arc of the work.
It's impossible, for me, to recall any other series that managed to mix King Arthur and the quest for the Holy Grail—in separate and unrelated episodes—or Gregorian Chant and Christian Monks—also in separate and unrelated episodes—with armageddon and venal politics and just what are we going to do about the telepaths, anyway?
But the Great Maker (J. Michael Straczynski) did just that. And there were assembled a cast of actors that took their characters and put flesh, muscle, bone on them—and took you along on a dance across a huge canvas that, nonetheless, hit home on a personal and human (notwithstanding the fact that half the main characters were not human) level.
I cannot say enough about this Science Fiction series. Storytelling, and story portrayal, at the Advanced Level, well deserving of the Hugo Awards it won.
Yes, there will be other series, on TV or in books or on the Big Screen. But some stories stand alone, for what they say and for how they say it.
Babylon 5 is one such.