Heh. You know, I too have railed against the stilted lines given the various Star Wars characters down through the years... but I think I know now that Lucas would not have it any other way. That's the way archetypes talk.
Yeah, the dialogue is definitely stilted. But I think that's at least partly because Star Wars is designed to be like a lot of popcorn movies and serials from the 40s and 50s. And anytime you watch movies from that period, you'll find that the dialogue is stilted in all of them. Movie acting was very "stagey" until a more naturalistic style of acting took hold in the late 60s. I think Lucas was partly mimicking that style. Of course, I think partly he just isn't as good a writer as he is a director, too
And just as a disclaimer, I'm not a Star Wars fan at all. I liked the first one a lot, after that they just didn't do anything for me.