The system is a D20, OSR-based system similar to Lion & Dragon. I think Pundit designed it to play Star Wars, but it would work well for Babylon 5 too. There's a class similar to Jedi, there are pilots, there are brawlers. All the good stuff. Races go by descriptive rather than name so you can easily adapt from one setting to another. Whether a "Contemplative" (race) is a Vulcan or a Minbari or a whatever, it's up to you (and your setting). There are 15 PC races that cover just about anything you could need.
Advancement is done in that neat random way that Pundit uses for L&D, not every character gets the same benefit upon "leveling up", which makes for fun progress.
As for the setting...
Babylon 5 is probably the best Sci-Fi show I've seen, and this is coming from a lifelong Trekkie. It follows a 5-year arc that builds upon itself and little things constantly pop back up from earlier episodes. Character development is incredible. This may seem common now, but in the early '90's this was unheard of. The Season 1 intro sets the stage:
"It was the dawn of the third age of mankind. Ten years after the Earth-Minbari war. The Babylon project was dream giving form. It's goal to prevent another war by creating a place where humans and aliens could work out their differences peacefully. It's a port of call. Home away from home for diplomas, hustlers, entrepreneurs, and wanders. Humans and aliens wrap in two million five hundred thousand tons of spinning metal, all alone in the night. It can be a dangerous place, but it's our last best hope for peace. This is the story of last of the Babylon stations. The year is 2258. The name of the place is Babylon 5."
There is plenty of action, of course, both fistfights/gunfights and starship/fighter battles. But there's so much more, as it deals with politics, corruption, power, history and religion. There are no robots/droids as characters - they're basically shown as tools and used for drone/remote work outside in space. But there are telepaths, there are super-aliens, there are ancient mysteries.
Gah, I don't feel like I can do the show justice in a short review. But one great line from early on in the show says a lot about the show:
G'Kar: "Let me pass on to you the one thing I've learned about this place. No one here is exactly what he appears. Not Mollari, not Delenn, not Sinclair, and not me."