TNG is definitely mt favorite Star Trek. I am working my way through DS9 season six, and by now I have realized that DS9 has zero chance of catching up to TNG. DS9 is more consistently watchable than TNG, but I remember a show for its great episodes, not its bad ones. DS9's best episodes are nowhere near TNG's best, and that's what decides the issue for me. If an album has great songs and bad songs, I simply skip the bad songs and listen to the great ones. Now, if you're proposing a watch-through of the entire show, the gap closes significantly, but I still prefer TNG by a comfortable margin. As for best of all time, TNG is in consideration with a handful of other shows. Hard to pick just one.