My favourite Deep space Nine episodes are the ones with Garak, that is really a good/bad guy according to the current circumstances, but he will look like a good one in the end, maybe...eh,eh
But Sisko is really a very good character, too, and he is only partly human in the story...eh,eh
About Battlestar Galactica: the New Edition, just have a look at Tricia Helfer as Number Six and you'll keep thinking of her...the same as Baltar does over the course of the series...
but is she real or not...eh,eh?
About Star Trek - TNG ( and Star Trek TV series in general...) I liked very much Data and Worf, but Picard remains to me one of the more inspirational characters of all time, I could say the same for Janeway, Tuvok and Sisko in a way...eh,eh
Best episodes ever, in my opinion of course: The Next Phase, Unification I and II, All Good Things I and II,and of course all, and I really mean it, the Q and Borg episodes surely!!! ;)