For this, you should take a list of major elements of ancient tragedy, and then go through the plays you have read in class to see whether the elements are or are not present.
Start by looking at staging. What are the main physical elements of the Greek theatre? How do modern stages differ from these?
What was the role of song and music in ancient theatre? Does it serve the same function -- or appear at all -- in the more recent plays you have read?
What about the use of verse vs. prose?
What sort of costumes were worn in ancient plays vs. modern?
Is there a limit to the number of actors in modern plays? What happened to the chorus? Why?
During which periods were plays based on an already known body of legendary stories? In what periods (and what genres) was invention ex nihilo more common?
What happens to the choice of characters (heroic/extraordinary vs. ordinary people)? What social classes were acceptable subjects for plays in which periods?