Since that's the Box Office Mojo list (
here it is in current form, Wikipedia's appears to not have been updated in a bit) it includes re-releases (which is a lot for popular movies made before the '70s. For example the numbers for
Star Wars includes the initial 1977 release, a re-release in 1982, and the Special Edition release in 1997).
While inflation adjusted lists are good at keeping a general sense of relative financial success of movies across time, they aren't nearly so precise as the numbers tend to imply. Especially since they rest on the faulty (and those who do it admit it's faulty) assumption that dividing gross by average ticket price gives a reasonably accurate total number of tickets sold. As an example, in 2008 both
Horton Hears a Who! and
Gran Torino had similar domestic grosses. But
Horton Hears a Who! probably sold at least 20% more (and possibly quite a bit more than that) because a huge percentage of its tickets were cheaper kids tickets and it played a lot better in suburban and rural areas where tickets are cheaper. But they'll forever be viewed as equally popular.
And then there are the intangibles such as what success means in 1939 for
Gone with the Wind when people knew that once it left their local theater town they might possibly never get another chance to see it again vs. now where everybody knows that they can watch the movie on their couch in six months and if they really wanted to pirate it a week early. Or that in 2009 there'll be four times as many movies released as in 1939.
But yeah, relative to society as a whole
Avatar will be nowhere near the all time top, but it will be in the top 25 which isn't all that bad.