How would number of tickets sold not be the best way to measure the popularity of movies during their theatrical runs?
1.) Value - Out of pocket hurt the wallet far less back in the day vs. today. The 'amount' for 2 people to go to a movie is far higher today.
2.) Options - Movies used to be the only game in town. If you don't see a film in the theater, you will most likely never see it. Now if you don't see it, wait a couple of months and it's out on BD, or Netflix, or OnDemand, or Premium Cable...
3.) Cost - It costs more for studios to make movies today. From explosive salaries because actors are no longer signed under contract by studios, to explosive SFX prices, films that draw audiences need to spend more. And the price reflects it.
That stuff is all irrelevant though. If you just wanna compare what kind of business two movies did you just wanna know how many people went and saw this movie and how many people went and saw that movie.
Like, Avatar is one of the highest grossing movies ever, but with the 3D surcharges it was also one of the most expensive movies to go see ever, so how is that meaningful data?