The other unique thing about B5 is the richness of character arcs. The central plot moves everything forward, but each character has their own multi-season arc inside it.
I mean, Garibaldi? G'Kar? Londo?
These are not "Oh, that's cute, the character changed" few episode arcs. They're the sum of innumerable small events in most episodes, that result in complete (and believable!) overhauls of the characters.