Look, I'm an in and out 9er, I think its the best Star Trek put on the small screen for me, by a country mile, but I respect that not everyone shares that opinion.
But to say its the best TV show ever?
I think its severely underrated by the general population and I think there's plenty of episodes that elevate it to being, definitely up there, but as an overall package, I think it does fall short to quite a few competitors, certainly Game of Thrones up to the end of Season 6 is IMO far superior, just as an example.
I think if you made DS9 today, fewer Episodes, higher production value per episode, more character development, set over the Dominion War, you'd have something truly special on your hands, but you would lose some stuff too, you couldn't do mirror universe, you couldn't do Far Beyond The Stars, so there's that to consider.