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.
I think you're really extrapolating from the 15-24 year-old hardcore MCU universe fanbase to all the casual movie goers out there. Most people can't tell the difference between Marvel and DC and would think Tony Stark is Batman's real name, or something.
Yes, no TV sets or VCR. That was pretty much the point I was making when I mentioned Star Wars. But... median household incomes were less than half of what they are right now in the developed world. Less free time (more industrial and agrarian jobs), less access to information and advertising. And world population and income out of the first world countries... proportionally even lower.
Even not taking into account all of that, what does that point would prove? Does it exculpate today's movie industry, or elevate its achievements for some reason? If anything, it only points out the movie industry never adapted and recovered its former stature.
Not sure what point you're trying to make talking adjusted by inflation. The meaningless one is the more correct, then, just because you like it more? Say, if there's eventually a short period of very high inflation, and a generic Michael Bay movie takes the top spot, even though it would have grossed less than half a billion if it released today, woud you say "Aha! New franchise to the top again!"
Actually, adjusting for inflation is actually kind to today's movies. To gross $3 billion worldwide today probably wouldn't even break the top 20 or top 15 in terms of tickets sold.