DS9 is vastly underrated, IMO. What makes it different from TNG is what makes it great. You have to appreciate each for what they are.
Getting way, way off topic here, but I think my dislike of DS9 stems from the fact I just really disliked the Bajoran story lines. The Dominion war was an epic bit of sci-fi storytelling, and the fact DS9s story was trotted out over the entire seven season run was historic for a sci-fi TV show. And the Dominion war/Wormhole was definitely a great storyline. I think I just disliked the Bajoran's since their story lines in TNG were weak, and it seemed like the Maquis took over TNG for a while as a means to promote DS9 inside of TNG. I just really, really didn't like the Bajoran religion and the Sisko as The Prophet stuff, but DS9 was easily the second best Trek series to TNG.
Like you said, each was extremely different, and I always enjoyed Trek from the exploration angle, which DS9 was clearly extremely weak in since it took place on a space station. Voyager could have and should have been my favorite by far due to the whole exploration of the unknown angle, but that show was a trainwreck from the get go. The Jeri Ryan lovefest since she was sleeping with one of the producers made it almost unwatchable towards the end. Never mind the fact they didn't get what made to Borg so great on TNG was the fact we only saw them once or twice a season. Borg every episode = no sense of a threat. Voyager was just a joke from S5 onward.
I love how Curly W cap sightings has turned into the WNFF geekdom/Trekkies thread. Next up:The Romulan Empire. Reintegration with Vulcan, or separate for all times?