Babylon 5 was great. It had great characters and spanned a huge galactic war that you actually feel the enormity of. In most sci-fi I've seen, massive wars are never really felt - you're just sort of told there's a big war on, and maybe see some generic footage of a battle. In B5 you see the subterfuge that goes on before war begins. You follow the entire military campaign, and the desperate diplomacy that goes on throughout. You see the political aftereffects of the war and how one can never really "win the war". There are hardly any fluff episodes in all of the 5 seasons. Nearly every episode advances the plot of the Shadow War to some degree. Damn, I think it's time for another Babylon 5 marathon!
I've got a Babylon 5 question for you guys. If you were going to introduce it to someone, would you force them to power through the first season, or is there a better place to get them hooked?
what I did was watch episodes that were important for the main story in Season 1. I basically followed what people said on here (http://scifi.stackexchange.com/questions/6370/what-1st-season-episodes-in-babylon-5-are-required-to-follow-the-main-arc) initially and I liked the main episodes so much I ended up going back and watching most of the rest of Season 1. So having someone watch 9 or 10 episodes to get a feel for the show is a good way to do it I think.
Babylon 5 has been one of the only shows, if not the only one, with a true speculative fiction (I can't really call it sci-fi as it had a lot of fantasy elements) feel for me. Most shows, good or bad, have sci-fi/fantasy as a window dressing but the implications of it all are rarely explored.