I'd dispute that it's the "most popular" - Star Trek is still defined more by Kirk and Spock than Picard and Data. The reboots were essentially remakes/adaptations of the original sixties show.
Three out of four TNG films didn't really work, so clearly the show was more suited to the TV than TOS. Discovery is the right way forward, something new rather than a remake.
I agree that, by and large, Star Trek is still fundamentally defined by TOS, but I think there's little dispute that TNG is the most popular in terms of the sheer number of people who consider that their favorite series. Every poll I've seen, and every anecdotal experience I've had has re-affirmed that TNG easily has the greatest number of fans. In terms of my personal enjoyment, I'd put TNG in third place behind DS9 and TOS, although I'm infinitely grateful for TNG keeping the torch lit for seven years and greatly expanding the Trek universe.
If nothing else, reading everyone's feelings in this thread shows how wildly differently we can each react to the same actors and material!
