My list is going to be TOS only. Every series that followed had too much padding during episodes. The first season of TNG was the worst. You would get 45 minutes of character development, then the adventure part in the final 10 minutes. Even the later seasons had long unnecessary scenes of Picard and the doctor having a long chat while drinking herbal tea, or someone complaining to Whoopi Goldberg about something for ten minutes. ( Interestingly, it was the only series with a psychiatrist, but you rarely ever saw any of the characters talking to Troi about their problems ). With TOS that weeks conflict began during the pre credit bumper, and didn't let up until the final scene. And there was rarely any character development padding. So yes, TOS was superior story telling to all the series that followed. And I can think of at least 48 TOS episodes that deserves to be on my top 25.
BTW, does the cartoon series count?