Looking
solely at the estimated ticket sales of the
original theatrical runs (no re-releases, no special editions), just the original theatrical runs and no spinoffs (Rogue One, Solo) is interesting:
* Box office records were not as closely followed in the OT time. I believe there is some data missing for ESB.
I think there is
something to say for the original three playing a role in the sales of the sequel trilogy but I think there are other aspects to consider as well and I think the numbers show it as well. First, the original trilogy was just at the cusp of home video coming onto the scene. While VHS was developed in the early 70s, it really didn't become affordable until the early 1980s. The original Star Wars wasn't released on home video until 1982 a whole
five years after it was released in theaters with Empire and Jedi being released in 1984 and 1986 (four and three years after their releases respectfully).
With the prequels, the release window was much shorter, with The Phantom Menace's first home release just eleven months after its theatrical release, and Attack of the Clones and Revenge of the Sith just six months after their theatrical releases. The release window shortened even further with the Sequel Trilogy as The Force Awakens and The Last Jedi being a little over three months each.
The relatively long theatrical engagement of the original Star Wars is impressive in itself and there are tales of people going and seeing the movie 20+ times in theaters. That is certainly saying something. I was only 3 when Return of the Jedi was first released so I know I only saw the initial run of one movie in theaters once. Starting with The Phantom Menace, I have seen all the saga films at least twice in theaters and on the end of things, I think I saw TPM four times. Bringing a movie home back in 1977 wasn't really a thought. Now with such a brief window of time between releases, a lot of people, even the die-hards will go and see the movie once or twice and wait to spend $20 on the blu-ray (or $25 on the UHD).
I think the proof will be in how The Rise of Skywalker does.
If it follows suit with the movies above, it will do better than The Last Jedi. That will say a lot considering both Hamill and Fisher's diminished roles (and Billy Dee's not-quite-member-of-the-big-three-status). Despite what the few hundred thousand members of the Fandom Menace might suggest, I think its possible to do so. However, realistically, if I was a betting man, I'm going to say that it comes in at 90% of the box office of Last Jedi.
The point being, its impossible to say how many people actually saw each movie in the theater (and how many followed suit on home video). But the number is significant.
To bring this back home, while the presence of the OT 3 possibly playing a part in the box office success of TFA and TLJ, I am doubtful that a high quality release of the original original trilogy will make $2 billion. It would do well for Disney. Just not
that kind of money.