Once DS9 got into the continuing story it got really good. The first couple of series were not that great for me.
Overall though, I prefer TNG. STar Trek is very character driven and they had the best characters for me. And some really stand out episodes, like Best of Both Worlds, The Inner Light, Yesterday's Enterprise, All Good Things..., Future Imperfect, Data's Day, Disaster, Conundrum, Cause and Effect, Chain of Command, Tapestry, Birthright (only the first part, though), Starship Mine, Parallels....and many more. In really kicked off once Roddenberry died, and stayed strong until the end.