As has been stated Lexx and B5 are two completely different animals.
I can't speak to an arc in Lexx, I never paid enough attention to get an arc out of it, but, what I did see, definitely seemed to have little more of a storytelling goal in mind, then the characters going from place to place trying to get laid.
Babylon 5 took itself very seriously (some think a little too seriously) and is my all time favorite series (behind it are ST: DS9 and Farscape).
One Day I hope to be the Man my Cat thinks I am
Where are we going? And why are we in this Handbasket?