I voted for 5, 6 and 7. Though I firmly believe DS9 was the best show there is from season 3 and onward, while also loving the first two seasons, I feel seasons 5 and 7, and to a lesser extent 6, presented with the very best of Modern Trek stories, stories richly textured, with a plethora of interesting and multi-dimensional characters.
So I'd rate them like this:
1) Season 5
By far the best season of DS9, and the third best season of Trek overall (following up only TOS's first two seasons). I can't think of one bad episode, except perhaps "Let He Who Is Without a Sin", which I still liked for the Jadzia-Worf interaction. Its got the best Trek crossover, which also happens to be my favorite episode in ALL Trek, and my favorite cliffhanger on the show. Also, Avery Brooks is simply great, giving a career best performance in "Rapture" and several others. Truly, a landmark season, and IMO the pinnacle of the show.
2) Season 7
This is my second favorite, despite Jadzia not being here and despite the fact that the first couple of episodes failed to register Jadzia's loss correctly (then again, they already missed their opportunity for an dramatic death for Jadzia, but anyway). Ezri is rather fine, and I much prefer Robert Wolfe's episode on her rather than "Prodigal Daughter". The war episodes are shining, not selling war or becoming overtly patriotic while still being interesting moral representations of pain and sadness in tmes of war. The Final Chapter is truly breathtaking, even if I'm not quite that crazy for the Dukat-Winn plot (which ultimately did lead to a lucklustre climax, but anyway). Worf killing Gowron and Damar killing his friend officer were highlights, and showcases of the pivotal changes that were due to happen by the end, and the finale was simply, smashing. Truly an undertaking of dramatic proportions, with the last 20 minutes really remembering the show in tears and sadness (I still miss Jadzia in these flashbacks, though). Overal, a great season.
3) Season 6
The first seven episodes of the eight-episode-arc of the overtaking and retaking of DS9 with Worf-Jadzia's wedding as its coda, is a great piece of storytelling, with only the Worf-Alexander story not holding as well as it should. Many good individual episodes really stick out, like Pale Moonlight and Far Beyond the Stars. But it has Profit and Lace, and it killed Jadzia is a ridiculous and anti-climatic manner - plus, "I felt that they had missed an opportunity for drama and for the emotional impact of her death. It felt rushed, and you really lost the chance for a goodbye scene that would leave the audience choked up," as Michael Piller very well put it, and thus, why its worse than 5 and 7. Still rather great, though.
4) Season 3
I just love this one - it has my favorite two-parter in this show, "Past Tense", and yet another one with Garak and Odo and Tain going at the Romulans and all. Also, the last good MU episode (all the rest just plain sucked), and generally its the time when DS9 grew out of its TNG shadow and became its own. The second season started the way, but Season 3 walked the path of the Prophets... Oops, I mean, it was awesome.
5) Season 4.
Worf comes aboard! An excellent move, in retrospect, as he grows and becomes more of an individual with his own voice rather than part of a group in which he rarely had a chance to stand out, as in TNG (though he still got the best episodes in TNG, but alas). Worf's coming only continued to grow the show's awesomeness to a new level, with personal stories that reflect difficult, tough choices for the sake of love. "The Visitor" and "Sons of Mogh" are prime examples of that, both showing difficult decisions of the main characters's part and a change in the secondary ones. Also, the best O'Brien Must Suffer episode is here, the Dominion-on-Earth plot playing out wonderfully, and in general a great turn out for all concerned. So why below season 3, if it continued to become better? My beef with it is the Klingon-Federation war, which went too long for no reason. In the end, it was pointless and despite the awesome episodes it presented, it was ultimately stalling for time, to re-introduces the Dominion threat as a more sneaky enemy. I don't hate it, I just like the season less than 3 for the K-F war as mentioned. Still a great one, though.
6) Season 2
A singnificant and apparent improvement over the first season, this has some real gems like "Necessary Evil", "Crossover" (best MU episode on DS9), the first three-episode arc in the beggining and "The Wire". Also, the Jem'Hadar are introduced, and thus, the Dominion, and all is well. The show was going to become something truly amazing, and it was all too apparent here.
7) Season 1
Quite obviously, the worst season of DS9. BUT, DS9's worst season is still a very, very fine season, with quite a few selections, the chief of which are Emmisary, Duet and The Hands of the Prophets, all of which are clear indications of whats to come on DS9. They're also some of the very best on the show's history. That said, several episodes drag too long, never ending satisfyingly and feeling as if the story got hanged up. And, several stories are trials that often work, often don't. Still, I am rather fond of this season, and for some reason, I can still watch as repeatedly as the rest of the, admittedly better seasons. Its just interesting, as DS9 was always.
Anyway, thats about it.
