Well, as far as the first Star Wars goes, it was the typical "Hero's Journey," as identified by Joseph Campbell. It is a damsel in distress, a young boy who sets out to get her (one we can all relate too), the rogue, and of course, the infamous villian. It's a classic tale retold with brilliant special effects and witty dialogue.

That being said, it's very hard to say what makes a movie "good." I'd go further with this but I have Econ on my brain much more than Star Wars at this point (school is ruining my college experience).