B5 is fantastic.
Let me start with the bad though: The CGI, especially the spaceship CGI in the first couple of seasons is bad. Really, really, really bad. Like listen, I have a high tolerance for bad scifi CGI (I watch Starhunter!) and I can tell you in some of the space battle scenes I literally can't keep track of what is happening sometimes. The CGI improves in the later seasons, but it goes from "I don't understand what I'm even seeing" to "Playstation 2 cutscene" level.
Ok, that's mainly it. If you can get past that, it is an amazing show. The most impressive thing it does is character growth. There are characters that you start out hating who end up becoming very sympathetic. There are characters who make face heel turns and it never feels unearned.
One amazing thing about the show is the running dispute between two alien races which is very similar to the Cardassians vs Bajorans in Star Trek Deep Space 9. To me, in DS9 I never really liked the Bajorans as a people, I know that I was supposed to but for various reasons I kind of just didn't care about them. In Babylon 5, I really care about the conflict and about the ambassadors from each species and what they are going through, and how their personal and professional relationship evolves. It was very smart to make the ugly alien reptile species the one which was being unjustly oppressed.
Without going on too much longer, the setting of the show is strong. You can see how dystopian earth is and how principled the main human cast is, and how every so often those distant dystopian tendrils from the earth government start reaching into the affairs of the show.
As a side note, if you like Star Trek TNG but don't like the "moral of the week" kind of thing, I do highly recommend Star Trek Deep Space 9. Great acting, very good effects that hold up well, and a fun cast of characters. A little slow in the beginning but once the main conflicts start kicking off it starts feeling very modern in how the story arcs are presented. Worf returns from TNG, but DS9 actually finds a purpose for his character and he really gets to shine.