B5 could have been the replacement for Trek as the biggest TV sci fi IP, but JMS and the studio just could not get along at all. Lots of good acting, though it sort of started slow because the first captain guy they had was literally going insane. Last Season had some solid stuff in it, but major issues were caused by the Ivanava actress spazzing out over "muh equal pay" and the fact that JMS tied up so much of the series when he felt it was going to be canceled after S4. It somewhat shared the same issues of DS9 where the secondary characters were so much better developed and acted than the central ones (Garabaldi, Lando, and J;Kar all crushed it in that show), though Sherridon had more charisma than Cisco right out of the gate. There were a lot of great story arcs with the recurring characters too, like the guy tending the great machine, Bester, and Marcus. The ending was not what it could have been, but I liked who was left running B5 and the arcs they set up. Too bad JMS was too angry to get much past Crusader S1 to do any of them.
Special effects I am willing to forgive (obviously I am a ST TOS fan) if the story is good and they serve the purpose. B5 met that criteria, even though it got a little far up its own ass at times with people engaging in hero worship at times. The whole buildup to Zahadun and Sherridan's return from the dead are pretty much the high point of the show, but you need what came before and after to truly appreciate the context of it all.
As far as JMS pre-storyboarding everything, that was mostly true with one major deviation. He had no idea how well the Lando and J;Kar relationship would play with the audience and how fucking good those actors were in those roles. Lando is probably my second favorite sci-fi character ever behind Elam Garrak from DS9. That dude just chewed scenery up like crazy. The original plan was for both those guys to die and their second fiddles to take over in those general roles, but luckily JMS changed course on that. Plus I think Viir had arguably one of the best character arcs in the entire course of the show and we would have been robbed of that had Lando not been there.