you keep jumping to arbitrary points while i bring up the simple truth of market stay power. thats what keeps the OT making money and the PT dwindling.
its absolutely true that TMP had an epic opening...but the reason for the later drop off is lost interest is film. simple as that. the current box office earnings are nothing more than a fizzle. you can grab for random issues which may affect sales. some people dont like wearing the glasses. the economy is rough. its not as old a film as the OT, etc. while these factors may affect sales by some percentage, collectively they are not the reason why few people are going to see it.
http://www.boxofficemojo.com/movies/?page=releases&id=starwars.htm