I think that a great TV show must have a solid plot.
Besides the plot, the characters should have depth, motives and ideals.
In my opinion the casting choice is also very important. Choosing the right actors may save a show's ratings.
Depending on the genre of the show, the creators must choose a fitting passing and length for the story.
The quality of the shows tend to deteriorate with time, therefore it is important to end while still being successful, in order not to deceive the fans with a lackluster finale.
