If you measure number of tickets sold and not movie gross (even adjusted for inflation, which it often isn't), Avatar is still only the 26th most popular movie ever. It's hard to imagine any movie, actually, any single media product, regardless of what it is (book, CD, videogame) ever coming within binocular viewing distance of Gone With the Wind, and that's fine. I am much happier with the diversity of entertainment options in this modern age and find most grumbling about the glory days of media past to be a function of clinging to outdated modes of production and distribution on the part of both artists and consumers.
Still, what has been impressive is Avatar's ability to get people to pony up $17, $18, even $20 a ticket to don 3-D glasses to watch a 3 hour movie. I had my doubts after seeing the extended trailer, but whatever its ultimate take, Avatar has become far more of a mainstream phenomenon than I imagined.