I'm nearly through Star Trek: Deep Space Nine (after having seen B5 in its entirety) and I've noticed a lot of similarities/parallels between the two series. I don't recall that there were any flagrant copies/rip-offs between the two series other than they are both set on a space station but then again why should only one show get to have a space station being a central focus for a series? I personally have enjoyed both series pretty much equally. Of the two series, I have always felt that B5 was kind of more "realistic" in terms of what the future would look like and more character-driven. It's continuity was a bit tighter than DS9 but then again DS9 didn't have the whole storyline planned out in advance. I still feel like DS9 choked a bit at the end with the final showdown between Dukat/Sisko/Winn, which seemed a bit "hammy", as well making the incomprehensible mistake of failing to resolve Bajor's status within the Federation, which underpinned the entire series. By contrast, I felt that B5 almost had no filler and wrapped up everything quite nicely by the end of S4 but still provided a nice little "coda" with S5. I'm planning to (someday) write up a blog post with all of the parallels/differences I've found between the two series.