This is a post in a series that goes back to my first post where I campaign against people referring to Star Wars as "A New Hope"
If I said "I live in New York" what would you think I meant? I live in New York state, New York City, New York County (Manhattan), or New York metro? Depending on the context you may think any of the four. Sometimes the meaning wouldn't be clear from context and you'd ask for clarification. A lot of the time it wouldn't matter, so you wouldn't bother.
One of the main arguments people make against saying "Star Wars" is that it isn't clear from context what you mean. But we tolerate the ambiguity with other words, like New York (mentioned here) and Disneyland (mentioned previously), so why not with Star Wars?
I bring up New York as an example because it has interesting parallels with Star Wars. For starters, for the most part, if people mean something to do with upstate New York they say upstate New York, not just New York. That is analogous to how you can specify that you mean a specific Star Wars movie you can give its name (e.g. Return of the Jedi), not just Star Wars. If people mean the entire state of New York, they usually say New York state, just like if you mean the Star Wars saga or trilogy you can say so. More interestingly, a lot of college students, I've noticed, mean Manhattan (that's pronounced Men-haten) when they say "New York." If you were talking about Queens or Brooklyn they wouldn't count that as New York City, I guess. That is probably a legacy of the fact that Brooklyn was an independent city until something like 1880 and Manhattan was just New York until then. Star Wars, of course, has a similar story, being released as "Star Wars" and being known only by that name for the longest time. (The 1981 re-release added the "Episode IV" and "A New Hope" lines to the crawl, but I don't think it was widely known until some smart asses started a trend in the 90s.)
One last point: you could take this as an argument for saying "A New Hope," after all it does seem stupid that people say "New York" when they mean Manhattan specifically. But Manhattan doesn't have a horribly ugly sound like "New Hope." And this is really about beauty as much as tradition.