carbons2k I think you should make the investment in watching DS9. If you watched all the rest, why not? I think you will find that many of the story themes are similar, but never have they been explored with greater depth, or attention to consequences, as they were on Deep Space Nine.
Example
You probably watched an episode of TNG called The Hunted, wherein a planet wants to join the Federation but the skeleton the closet is the way they treat their ex-soldiers. Good episode. I loved it, especially the end of it, where Picard said that if the government "survives the night," he will recommend their inclusion to the Federation. It ends with Picard believing that he thinks they will survive, out of force of will and out of the need to resolve the issue, and, poetically, the big E rides off into the sunset. The episode works by having us believe that the government did survive, and that we really don't need to actually know for sure for the point of the story to shine through.
Now imagine if we actually got to see if the government survived the night. Imagine if we got to remain on or near the planet as the real, delicate issues were resolved over time, and you didn't have the option of just flying away to next week's planet.
If that was the case, the show you would be watching would be Deep Space Nine. Throw in some non-Starfleet officers, some pressing moral dilemmas, villains that are not even really villains, (Garek and Dukat are more well-rounded as guest stars than any of the major players on Voyager and most of the other characters on any of the other of the other Star Trek shows) add political strife, paranoia, war, comedy, a little spying and intrigue, and you have a recipe for a great show. Not just a great show, but a show that will challenge you. If you are so used to all the other series and have not watched DS9, I can assume that you have yet to be really challenged by Trek. Maybe the heroic Federation isn't always right, and maybe that makes the stories DS9 tells more interesting.