The 'DS9 copied B5' argument is pretty ridiculous. It's not like a show on a space station that's serialized is a super-obscure idea two different groups couldn't possibly come up with on their own. It's like how South Park did an episode about pretending to be handicapped to cheat in the Special Olympics, then a crappy movie came out with the same premise. All the South Park fans said "The movie copied South Park!" Then the South Park creators said "No, they totally didn't copy us, it's just a really obvious idea."
A space station was a logical progression of the space opera genre that naturally lends itself to serial storylines which the hardcore end of the scifi fanbase was aching for at that point.
And B5 may have had an awesome main plot, but if you take any individual incident out of the context of the main plot, it suddenly looks really silly, whereas a majority of DS9 stories stand on their own in addition to being part of a great main plot.
But did DS9 really influence other scifi or was it just a good scifi series in a style that was just starting to become popular?