I give props to Mat001, but I've read a lot of interviews where Lucas admitted he goofed off, padded the story and ran out of time for the prequels and the OT had a lot of collaboration. Hell, a 2010 interview with Jon Stewars has him answer a question with "I didn't think of that."
Lucas thought about very cool concepts, but ultimately had no idea how many things would fit in the long run. The differences are there and yes, you can overlook them and still enjoy the story.
But if he had kept it as tight as it could have been kept, it would have been the perfect saga.
Which is why I'm hopeful about the new movies. Keep it tight, gentlemen, and you got it made.