Babylon 5 was a ground-breaking science fiction series, the first to utilize a multi-season story arc for its entire run. It was written and plotted from the start as a "novel for television", with a clear beginning, middle and end. Moreover, it was a visual effects pioneer, being shot in th cinematic 16:9 rather than the standard 4:3 of TV, and all the visual effects were completely computer generated (CGI) at a time when models were still the standard.
In setting, Babylon 5 was also atypical, a change from its predecessors, in that it dealt not with a utopian society coming to grips with nature and the unknown, but with inherently flawed humans and aliens, their problems and conflicts, hatreds and likes. Others have followed suit, but Babylon 5 was the first.
There are conspiracies of light and shadow, choices made and consequences faced. For all the serious plot lines, there are plenty of moments of humor to lighten the mood.