The idea behind the show was a great one; it was to run for five years, and in those five years tell one, big, self contained story with a clear beginning, middle, and end; and by the time we got to that end that would be it. That's where the story ends, and there would be no loose ends...
(Of course, mice and men intervened; Season 5 was, for about 2/3 of it somewhat below par, there were loads of loose ends, some left deliberately to set up a spin off series which only managed half a season, and a movie that never happened... Anyway...)
At the point Babylon 5 started, TV sci-fi series were pretty much just a string of separate stories, with episodes that could (with odd exceptions) be watched in pretty much any order. They were designed so that you could turn on an episode and watch a complete story in 45 minutes. Babylon 5, initially, appeared to follow the same pattern, as many of the early episodes did tell complete stories. There were some obvious threads running through the episodes - such as the hole in Sinclair's mind, and why the Minbari surrendered when on the brink of victory in their war against Earth - but these were background. However, pretty soon this changed and B5 pretty much became a serial. I hesitate to use the phrase "sci-fi soap opera", as that will stir up negative connotations in people's minds, but that's more or less what it was.
There were turning points in the first season; the sixth episode, Mind War, introduces us to the Psi-Corps, and the wonderful Mr Bester, played with a chilling menace by Walter Koenig. You always knew you were in for a treat when he turned up... but the biggest shocker in this episode was the glimpse at the end of a creature not seen for thousands of years... just the briefest of appearances, but enough to make you think there is much more going on here than we know of.
This would be expanded further in the biggest turning point of all in the season, Signs and Portents, in which a mysterious man, Morden, arrives on the station and goes to the main ambassadors asking them one, simple, question; what do you want? (Of course; that question is at the core of all drama. Remind me to tell you about that one day.) It is their reaction to this question that shapes the entire future of the show. It is Londo Molarri of the Centauri Republic who Morden, and his associates, ends up allying with, doing Londo a favour with a promise that somewhere along the line, Londo will do one for him... Faust, anyone? When we see his associates at the end of the episode, and what they can do... we know there's only one way this will end; in fire.
Mention of Londo brings me to, what in my mind, was the best thing about the show. The relationship between Londo and G'Kar. The changing relationship between these two characters over the course of the show was a joy to behold. Every time they had scenes together the screen was on fire. Episodes that were humdrum and run of the mill were elevated just because they had scenes together (the "mad bomber" episode, for example, is completely redeemed by the scene when the two of them are trapped in a lift. G'kar's reaction is priceless.). This is largely due to the fact that the actors portraying them were so great; Peter Jurasik and, the late, Andreas Katsulas were just perfect. They sparked off each other brilliantly, no matter what was asked of them. There is a scene, in a bar, in the season two episode The Coming of Shadows where this is exemplified; Jurasik has hardly any lines in the scene, almost everything about his performance is conveyed by the expression on his face, he doesn't need to say anything. It's all there.
Now, I could go on and write a couple of dozen more paragraphs about how great the show is, and wonderful scenes, and moments that will make you cry, and moments that will make you laugh... but if you've seen the show before, you'll know them. If you haven't I'll end up spoiling it for you.
And, if you've not seen it; get it. But, be warned; don't bother with the TV movies or Crusade. Just watch the 111 episodes from The Gathering to Sleeping in Light.
Thinking back to how eager I was to see each new episode, it's really like how I feel right now with Lost. I'm just so keen to see these last 18 episodes. And the anticipation and speculation as to what will happen next. And the spoiler avoidance... oh, it's going to be fun...
...but when it's all over; what then...?