(Note: I tried to update the OP and it wouldn't take, so I'll just do this in a reply post.)
Endgame is already the biggest film of the year, with the largest opening of any film in history. In fact, it took only 16 days to become the most successful film in the MCU, and 17 days to become the #3 film of the 21st century (adjusted for inflation, of course). But how exactly did it fare after it's historic opening? Let's consult the charts, comparing it to its predecessor as well as the top two films of the 21st century:
Endgame's historic opening weekend did not translate to equally record-setting numbers elsewhere, though its numbers were still quite strong. Its first Monday-Thursday period was still the second-best of any 21st century film, as was its second weekend (and that's with TFA having Christmas day on Friday of its second weekend). But after the second weekend Endgame started experiencing a much larger drop-off than TFA did, and it's clear at this point that Endgame has no chance of taking the #1 spot for the 21st century domestic box office. In fact, it's trajectory from its 11th day onward has very closely matched that of Infinity War. The Week 3 figure in the weekly chart (which assumes yesterday was down 55% from last Thursday; the final number may be slightly different, though unlikely to move the bar for the week visibly) puts Endgame at about $81M, only slightly ahead of Infinity War's third week, just slightly behind first Avengers' third week, and considerably behind TFA and Avatar's third week. It's third weekend ranks only #6 among all third weekends, bested not only by TFA and Avatar but also by Sam Raimi's Spider-Man, Titanic, and Black Panther.
While beating The Force Awakens is out of the question, Endgame still has a chance to pass Avatar's inflation-adjusted gross. It's still running a significant LTD lead over Avatar, though that lead is slowly shrinking, as shown in this chart:
Avatar didn't start off strongly, but its box office performance was a slow burn, more closely resembling what we saw with films back in the 20th century when there was less focus on the opening weekend. While most films these days often make 85-90% of their lifetime gross in the first four weeks, Avatar made only made 60% of its lifetime gross in its first four weeks, grossing over $339M after its fourth week, more than any other 21st century film. It was still making decent money three months after its release, a point when most other blockbuster films this century would have mostly fallen off the box office radar. Avatar's 12th weekend was the 14th largest when adjusted for inflation, while TFA's 12th weekend ranks #156. This means that Endgame may possibly end up falling short of Avatar. After three weeks, Endgame is running an estimated lead of about $296M ahead of Avatar, while Avatar made $418.6M after its third week. That means that Endgame needs to gross about $123M from Week 4 onward. If it can somehow manage to make at least 13% more after Week 3 than Infinity War did after its third week, it could pull it off, but most likely Endgame may fall just short of Avatar's adjusted domestic gross.
Endgame may have had the best start of any film ever, but it's legs haven't been anything exceptional, relatively speaking. Nevertheless, it's overall success cannot be underestimated. It's already the most successful film of its genre (superhero/comic book adaptation), and as mentioned it took only 17 days to become the #3 movie of this century. It's currently #13 among all films of the "Blockbuster Era" of cinema (generally considered to have begun in 1975 with the release of Jaws), and is still making money, enough to where it'll end up at either #7 or #8 (depending on if it can pass Avatar).
Globally, Endgame has done exceptionally as well. It stands a very good chance of passing Avatar's global box office figures. It needs to make only about $257M more; assuming its gross from Week 4 onward is still a 30/70 split between domestic and overseas, then further assuming ~$110M domestic from here on it should gross an additional $250M overseas for a total of about $360M, more than what it needs to pass Avatar. Granted, Avatar is a decade-old film now (which makes me feel even older...) and it is likely to have made more globally adjusted, but it's impractical for anyone to calculate its inflation-adjusted global gross (we're talking dozens of currencies to take into account) so we may never no for sure if Endgame "truly" was the more successful film globally, but by any standard Endgame has been a global phenomenon. It may not become the first $3 billion movie, but what it's made now after just three weeks has been nothing short of stellar.Last edited by Shadow1980 - on 17 May 2019