The characters plus the whole development of the series.
I must admit that my Deep Space Nine watching was severly hampered by stupid politics of a certain TV station where I live.
I only got the opportunity to watch season 1 before the station decided to stop airing the show. After that I could only watch a few episodes from season 2, 3 and 4 which a friend of mine had bought on videotapes which meant that I didn't get a particularily good grip on what was happening in the series.
As for the first season, I thought that the characters were OK but not more than that, sort of TNG.s minor team if we compare with sports leagues.
But when I finally got the opportunity to watch the whole series from start to end in the three recent years, then I finally could see how the characters developed and how the series itself progressed during the years.
From the start I liked Quark and kira and they remained among my top favorites.
But characters like Jadzia Dax, O'Brien and Bashir who I initially thought was rather good but not more became even more liked by me during the series. Sisko, who I thought was a bit wooden in the beginning became a real force of power during the series. he could be a real bada** too! I also liked the interaction between Bashir and O'Brien.
Garak who I thought would be just a recurring character became an absolute favorite as the series progressed. I really like Garak's way of behaving and his witty remarks and he's my second favorite in the series after Quark. I've always liked that kind of characters who can be somewhat mean and manipulative despite being the good guys. In fact, when it comes to garak, it took some time before I realized that he actually was a good guy and not a Cardassian spy on the station.
And even Jake Sisko who I thought was a weak character had a lot of good episodes and grew on me during the series.
Ezri was also a great character. Unfortunately she only got one season. I must admit that I didn't like that Jadzia was killed off. I would have liked to see her being transferred to Enterprise and Ezri could have come on board as her sister or something like that.
The only character I had some doubts about was Worf which is strange because I really liked him in TNG. He was OK in DS9 but not as good as in TNG. It was as if he really didn't belong in DS9.
The progress and development of the series was also brilliant. It started with the Cardassian-Bajoran conflict but developed into much more with the Dominion and all that, not to mention different subplots which occured during the way, the weirdest was when the Federation almost started a war against their allies, the Klingons in a futile attempt to protect the Cardassians.
The series also had an some excellent "bad guys". The female Founder became a real hate object for me during the series. A real monster! But as much as I hated the character, I also found her a great villain.
I really liked Kai Winn and Gul Dukat. Excellent villains. Winn who had a striking resembly to an old aunt of mine was excellent with her manipulation and hunger for power. Dukat was a brilliant "bad guy". Arrogant, mean and manipulative.
And don't forget the slimy Weyoun. Sometimes he really annoyed me, sometimes I just had to laugh at him.
I would also like to mention the Cardassians which I consider better villains than the Borg. The Cardassians were no super-beings with super thecnology who it was necessary to win over with even stronger super-powers. Their strength as villains was their way to be cruel and manipulative. The interesting thing with this species was that in the last season they became almost likeable due to the way they were cheated and manipulated by The Dominion and therefore finally rebelled against them.
As for DS9 being "dark", well it was darker than TOS, TNG and Voyager but not as dark as it became boring and annoying. OK, the Federation-Dominion war was heavy to watch sometimes and maybe it shouldn't have dragged on for three whole seasons. But it don't affect my overall positive impression of the series
Deespite that, there were always some lighter episodes here and there which lifted the mood and that was enlightning.
All that made DS9 to a real fantastic series to watch.
I must also add something which did strike me when I discussed the Star Trek series this summer with a relative who also happen to be a fanatic rock music fan.
If TOS was like Elvis who started the whole thing, then TNG was Beatles who came up with something unique which started a worldwide phenomenon. DS9 was like Rolling Stones, same genre but still different while Voyager was like The Who, Animals or Yardbirds with an own style and a small but dedicated fanbase.
