I'd slap down fully 1/3 of TOS as worth viewing by anyone. In watching every episode of every sequel, I found most of the first 3 years of TNG abysmal, DS9 interesting but lightweight (with occasional exceptions like "Duet"), Voyager kind of tedious, Enterprise…well, why go on? Compare the average level of any post-TOS "socially relevant" script with that maintained week in and out by Babylon 5 or the Galactica reboot, and I'll think you find the former lacking. Fun? Sure. Pretty? Yep. Decent in SF terms? Sometimes. But "deep"? Hah. Now compare TOS with its contemporaries…and consider that it still stands up today. I hold that TOS outshines all its sequels, which far from pushing the envelope conceptually or contemporary-comment wise, came off as sophomoric compared to what was THEN on non-SF TV.