Babylon 5 WAS, BAR NONE, the best sci fi series I have ever seen...
If you ignore the first season, that is...
They developed a long term plotline and stuck to it... so instead of stand alone mini stories you had a fairly well thought out epic.
The first season sucked so bad that I stopped watching it after a few episodes, I didn't start watching regularly until near the end of the second season, after that I was hooked- it was incredible... It had flaws, but its exceptional story and striving for realism made up for the flaws.
I would say that it was the only tv show I ever made a real effort to catch when it aired...
Star treck DS9 was a DISTANT second when it came to quality sci Fi...