The only DS9 relationships I liked were:
1. Miles and Keiko. Pretty realistic of a typical marriage I would say. They are a carryover from TNG though.
2. Bashir and the autistic augmented girl, even if it in the end was really one sided (his feelings for her were real).
I think that's it.
Odo is a changeling. He does not have sex. He links up telepathically (or however they do it) with their own race. The mere notion that he can have attraction for solids is beyond stupid. The whole reason the Federation was saved is because Odo bagged Kira (she never really liked him that much either). Otherwise, Odo would have defected and betrayed the Alpha Quadrant.
Jadzia was a bitch!! I could not see a damn thing that Bashir was attracted to her for. Of course she falls for Worf, the jock football player character, and they get to beat each other up during sex

Not to mention a "Beauty and the Beast" allusion happening here.
I could see Sisko and Cassidy together, but their acting never sold me out on their love. But I'd have to watch the series again to judge fairly as I pretty much tuned out to their story.
And Leeta/Rom. Well, another "Beauty and the Beast", except this time it's the "quirky beautiful chick falls in love with the ugly kid because of his personality". I do admit it did work somehow, but only because Leeta was supposed to be an airhead, and Rom was so friggin' likeable he could have been Jabba the Hut and you'd still like him. As played out in the series it worked well, but why couldn't DS9, calling itself a better Trek than Trek, do something actually out there, like having a handsome Starfleet or Bajoran man fall in love with an ugly alien girl, because of her personality? Show didn't have the balls to do it?