Surprised I missed this one. The subject, not Babylon 5.
What as significant about the series was proving that not all SF TV was Star Trek.
The first season was really to establish all the various sub-plots and alliances before Straczynski turned a lot of it on its head making the Narns more heroic and the Centauri the bad guys. Even the position of the Vorlons was played down until season 4.
For Season One, 'Parliament Of Dreams' has to be my idea of the perfect episode with multiple twists.