I always thought that B5 had more in common with Lord of the Rings than DS9.
I was waiting for someone to say that.
Another thing people aren't mentioning (it may be later in the thread) is the serial nature of the DS9 story. Trek was really a bottle-type of show where the universe was largely the same after as before. B5 was designed with one long "arc". Some episodes could stand alone and had little "arc" material, but those tended to be the weakest. The innovation, the "draw" of B5 was the "arc" and that is what DS9 started to do more and more as the series went on, where you really had to tune in each week to follow what was happening. So my feeling is that DS9 saw how B5 was earning, if not ratings, at least critical praise for the "arc" and how it made B5 feel "epic" and decided to make the serial story format more prominent.
And sure enough, later on serial-type stories like Lost, Battlestar Remake, etc... are the standard rather than the exception with A-list 1-hour dramas.
The trend for serialized A-list drama begins in the 80s with shows like Hill Street Blues
, St Elsewhere
and LA Law
. It was a trend that Star Trek was already behind on. I think those shows had a bigger impact on the people behind DS9
going for serialized story telling than B5