How would number of tickets sold not be the best way to measure the popularity of movies during their theatrical runs?
Population is a lot bigger nowadays, so more available eyes. Entertainment choices are more vast now. Back then, if you wanted to see a movie, seeing it at the theater was the only choice. More competition now.
The most meaningful metric would be probably be to compare and tabulate the numbers for the movies in a specified year (Attendance, box office take, profit) and see what percentages of the total your specific movie that you want to compare to accomplished. Then do the same thing with the other movie you want to compare
GWTW made $100
GWTW sold 100 tickets
Total Box office for year was $1000
Total tickets sold in the year was 1000
GWTW took 10% of Total Box Office
GWTW sold 10% of the tickets sold that year
Do the same with profit
Then do the same for the movie you are comparing it to, and see how they measure up
Even this has it's problems, but, it's closer, IMHO