My thoughts on Deep Space Nine are as follows:
The show started out kind of different and interesting. But then after a couple seasons, they started to lose confidence in DS9 and started doing everything it could to make it more like TNG. For example, bringing in Worf and thusly, the entire Klingon story ark from TNG. Sisko now had to be made a Captain and given his own little starship, so that the base is just a platform, more or less for the Defiant and its exploits. Bringing back all of these TNG elements and making DS9 fall more in line with traditional STAR TREK really hurt its claims to being a "unique" series.