Did you see the other posts? Gone With the Wind was first and it still is. Only James Cameron and the first Star Wars came close.
ESB made more money than ANH on their respective first runs. But ANH got tons of re-releases and lingered in theaters for many years, specially before its sequel came out, while ESB didn't. It was a different time, with a different kind of movie-going culture. One that had all but waned by the early to mid 80s. Some blame it in VHS and cable TV, but it happened before VHS was really popular.
And you seem to presume there is a single audience block interested in all Marvel movies who has stuck with it from the beginning. But these 22 movies have wildly different stories, characters and box office incomes. And a very thin plot thread binding them all together (which often doesn't appear until after the credits!). The crossover events, and specially the two Avenger Thanos movies, are just where they managed to gather all these disparaging audiences together. It makes sense, considering these movies could end with the death or their favorite characters.
You would have a point, there, if these movies were called Avengers 1 to 22.
Well, Gone With the Wind is only first when adjusted for inflation (which is not the proper ranking), in domestic (US) only. At that time television sets werent a real thing, you HAD to go to local theatre/drive-in to see it, not just skip so you can binge it later on netflix. No VCR, no DVD, no nothing.
Still my point stands, before Endgame it was always original movies that held that #1 spot
And there is a HUGE overlap between the audience of the movies. Everyone now knows what "MCU" means, and is effectively treated as a franchise by a huge audience now.
Bet with Intrinsic:
The Switch will outsell 3DS (based on VGchartz numbers), according to me, while Intrinsic thinks the opposite will hold true. One month avatar control for the loser's avatar.