Favorite episode? That is a difficult one, it would be easier to pick the handful I didn't care for that to pick the one episode, or even one for each season I really liked.
Here goes, "Severed Dreams" would definetly have to be near the top. Loved the way Delenn came out in the nick of time and her response to the attackers. Then there is the episode where they free earth. Never forget the Agemmenon taking out that defense platform.
On the lighter side there was Bo and Mack. That was a great episode, a chance to see things on the station from a working class perspective.
As for movies, loved Call to Arms, and IN the Beginning. River of souls was okay but I wasn't a big fan of Thirdspace.
As to Crusade, I think the show had a lot of potential. For those who didn't care for it remember the episodes where shown out of order, TNT kept interfering with the way JMS wanted it and the first season of any show is one of the main one for the characters to be built. Rewatching the first B5 episodes then the last ones you can see the change in the developent in characters. A change which never had a chance to develop in Crusade. I think if JMS had been left alone to do it the way he wanted and Crusade had been given a chance it would have been right up there with B5.