"Box Office Mojo"
Release Schedule
Box Office Mojo Announces New Release Date Of 'One for the Money
Box Office Mojo has listed the top grossing movies of all time
If you really want to gauge cultural impact, you'd have to adjust the list further according to US population at the time -- when GONE WITH THE WIND hit theaters, the country was half the size it is now. But this is a heck of a lot better than the un-adjusted list.