If you adjust for production costs then you're no longer talking about gross. Adjusting for inflation makes sense. What would be even moree interesting would be an analysis of which movies are "evergreens" (http://www.airwindows.com/analysis/Evergreens.html) -- long-term moneymakers, classics -- though the differences in the way music albums and movies are marketed and consumed would make such a determination for movies less straightforward than for albums.
(no subject)