DS9 may contain some of the most exhilarating & frightening moments in the Star Trek franchise, but it also appears flawed in its drawing of its main character, Benjamin Sisko. played by Avery Brooks in a frustrating & somewhat jarring performance.
Where Star Trek (original) blurred the lines between diplomacy & action true to 1960's ethics & was then ably followed by TNG (with a stellar turn from Patrick Stewart as Jean Luc Picard) in a show that firmly established Star Trek as something to be taken seriously. Now we have had years of further developments, more Captains on show & more elaborate plot-lines. But DS9 remains the last great Star Trek effort, despite the heavy-breathing, shouting Sisko!
Seriously good actors such as Patrick Stewart do not drop off trees & even if they did they would probably run a mile from such a series. DS9 is saved from too many excesses by its superb story; a stationary space station full of differing cultures where elements external & within shape the action & also in later seasons its producers were left to pursue the idea of a grand war (with the Dominion) despite Rick Berman's objections. Berman left DS9 to oversea the mediocre Voyager series that contained a reasonable contestant (Kate Mulgrew) for the golden gong of most annoying Captain, with Benjamin Sisko (Avery Brooks).
So, in all DS9 is an excellent series that contains some of Star Treks most memorable characters; Quark, Garak, Gul Dukat, Odo, Rom as well as a reappearance from Worf. It's a lengthy 7 seasons to get through & like its predecessor it suffers from the occasional blip (but in all honesty, rather less so than The Next Generation). Nevertheless, Deep Space Nine is thus far the last great Star Trek series, despite the protestations for those who claim Voyager to be so, or for that matter, Enterprise.