Differences in Interpretations of the King Arthur Myth

As I was reading Geoffrey of Monmouth's portrayal of Arthur, I could not help but wonder how and why the legend of King Arthur was spread and how is this different from the myth that we know today?  According to the introduction given before the excerpts from Geoffrey of Monmouth's work, this was the first point in Medieval History that King Arthur was mentioned.  In books I have read and in movies, I have always seen King Arthur as this great and noble king that is guided my Merlin the Sorcerer and the knights of the round table.  Geoffrey's account of Arthur shows him to be somewhat self centered and war hungry; he is always going into battle to conquer distant lands motivated by his own interests and religious fervor.

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