Whenever they proclaim a film as "most revenue of all time" they really ought to do that analysis in inflation adjusted dollars.
Titanic's $2,243,134,099 in 1997, is equivalent to ~ $4,155,000,000 today. (imperfect number, because not all of Titanics ticket sales occurred in 1997)
These comparisons are useless unless adjusted for inflation.
It is also probably appropriate to adjust for physical sales vs streaming etc. for older titles, as some stuff is historically included, and other things not.
The industry intentionally avoids adjusting for inflation, because they want to continue to brag about increasing sales and revenues, even when that isn't necessarily the case.
IMDB tries to maintain a list of top grossing films by inflation adjusted dollars:
(Including Re-Releases) (Some adjusted values could be higher or lower because the calculation for old movies is very difficult)
www.imdb.com
If we look at this, it looks like the film industry peaked in 1939 with "Gone with the Wind". They can't have that.
The Moist Avatar doesn't even rank in the top 10, coming in at #15.
Also, say what you want about James Cameron. I tend to think most of his films are crap, but he does have a knack for hitting the lowest common denominator of "broad appeal" such that the money comes flowing in, and there is value in that. While the film industry is part art, it is also a business, and it needs to run a profit.