It was a slow transition IIRC. The original boxes used big names and little names (giant and small font). Originally, they were either STAR WARS or STAR WARS/A New Hope, Star Wars/THE EMPIRE STRIKES BACK, and Star Wars/RETURN OF THE JEDI. Then around the time of the faces set, they switched to Star Wars/A NEW HOPE, Star Wars/THE EMPIRE STRIKES BACK, and Star Wars/RETURN OF THE JEDI. I don’t think they ever called it A New Hope without also including Star Wars.
It’s hard to say whether this was because they wanted to include the series title on all films (which makes sense), or because they didn’t want to confuse fans who wouldn’t know what “A New Hope” was and were just looking for “Star Wars” (which also makes sense).
And episode numbers. Hell, I stopped paying attention to packaging long before they started putting episode numbers prominently on them. I imagine they’d start doing that to improve the relevance of the prequels.
Man, I remember being 8 years old in 1993, watching Star Wars on VHS. It always confused the hell out of me that the first movie was called Episode IV in the title crawl. Lucas is a madman.
When watching Empire in the theatre in 1980, audiences were shocked that it jumped to Episode V, leaving kids like me to wonder what might have happened in the three episodes they skipped between Star Wars and Empire.