I understand that Lucas may have not ripped off the idea straight from the story of Superman. I do know that he's used other plotlines, stories and characters as a foundation for his own. For example; James Bond was an inspiration for Indiana Jones, and I read somewhere that Robin Hood was a pre-concept for the character of Han Solo. I believe it was Nitsche who stated there is no such thing as an original idea. As a writer myself, I understand that borrowing ideas is not plagiarizing nor stealing, I just find it interesting when two separate stories coincide almost identically, yet have an almost totally different outcome.