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.