I've never seen Babylon 5, so I cannot speak for its quality. What I can tell you, is Farscape is by far the greatest sci-fi show I've watched in my life. It doesn't have the franchise or geek appeal as Star Trek, but it is an emotional rollercoaster through the lives of an unlikely crew. You very clearly watch all the characters develop, and see through the eyes of John as he loses his mind during their adventures. It can be a bit over-the-top at times, but it more then makes up for it with excellent acting, and writing.
I cannot tell you if Babylon 5 is good or not, but I can tell you that if you watch Farscape, you won't be disappointed. Farscape is also on Netflix instant-view, if you have a computer or TV capable of streaming it. It will probably be higher quality then a DVD, as well. They may not have season 4 (About two years ago when I watched it), but seasons 1-3 I know are on there.
EDIT: Oh wow, I did not know how long and old this thread was, so I was responding to the original post. My bad xD.