When did we start identifying "Star Trek" as a franchise. TNG was a spinoff show of the original/movies, and there's been other spin off shows that didn't make something a franchise.
As for Heart of Glory being the best Klingon show, this is really a matter of taste. HOG is a great episode, but I've always enjoyed the political intrigue that Star Trek offered, be it in TNG or to a larger extent DS9. Heart of Glory is a great pure Klingon show though, and probably when it came to culture, the best one. I really didn't like the Klingon Culture/Alexander episodes that came after Sins. They were all a little on the boring side.