Babylon 5 was a whole new ballpark when it came out in the early 90's. Good television is now everywhere, but when B5 came out, it was completely unconventional to have a continuous plot over five seasons. At the time "one plot per episode" was the accepted standard, and while the dramatic arcs of for example Star Trek, the Next Generation (ST:TNG) eventually became longer as the script writers got more confident, the arcs of B5 were supposed to last through the seasons from the beginning.

The writing is occassionally weak, and thus it pales in comparison to more younger fantasy productions like Battlestar Galactica reboot, or Game of Thrones. But at it's time it was groundbreaking.

The moments of epic were really good since they were preplanned and they could be foreshadowed much in advance. Hence moments like (spoiler alert...)

... Earth falling into totalitarian state, bombing of one of the alien homeworld, the Shadows overwhelming Centauri prime, etc, were nearly unheard of narrative high points due to the buildup to them over the series.

There were lot of not-so-high quality filler episodes and so on, which make the series more of a cult classic rather than ... an obvious classic.

And yes, I categorized space opera as fantasy :)