I liked season 5... or rather the underlying plot through out it. The final fall of Centauri prime, the issues of an interplanetary alliance, ancient technology in the hands of younger races, the end of Londo's arc, Lyta - G'karr story, Garabaldi taking Edgar's industries, Number 1 working for the Rangers...
I think it's better than people give it credit for. Also, we all have to remember that there wasn't even going to BE a 5th season. WB was skeptical so he cleaned up the Shadow War really quickly and blew through the Civil war (which was supposed to be the final arc of season 5).
Crusade... I'll be honest... I really didn't get to see much of it. It was on at an extremely inconvienient time and only ran once or twice... so I missed most of it. I have been meaning to get the DVDs, but come this Xmas I will finish my B5 collection with season 1 (woot!).
I am amazed at the pesimism (I can't spell for beans) I see around B5 forums over these "Lost Tales". Yes, LotR did suck ass... but I always felt he didn't have the control over it like he normally would... though the acting is what REALLY killed it.
I am usually a pescimist (does this look more "right"?) by nature, but in the end I think we are going to be pleasently surprised with these.