There's estimated ticket sales based on yearly average ticket price which is about as good as it gets for that.
https://www.boxofficemojo.com/alltime/adjusted.htm?adjust_yr=1
Avengers End Game is currently sitting in 34th all time at 73 million tickets, The Force Awakens finished with 108+ million, Avatar has 97.3 million, Titanic has a whopping 135.5 million. I believe these are domestic.
Nothing is touching Titanic in the modern era most likely for people who actually went to the theater or butts in the seat as it were.