TNG was perfect as a seasonal episodic show. But is "too smart" for movies. And it's main characters were all a bit too old to fit in with that crowed of characters.
TOS is perfect as both. Plus on the Show and the Reboot it's characters are the perfect age for "action adventure" type stuff. I think of TOS well the movies for the most part to be Space Adventure Epic's where TNG is a Timly Space Journey Adventure.
TOS has the best stuff to make a movie. TNG has the best stuff to make a TV Show.
If that makes any sense.