What effect did King Arthur have on literature?

That is a complicated question, because most people believe that King Arthur has no basis is historical fact, but is actually just a part of literature... a fable. Not to say that a fable can't have an impact on literature, because lots of people picked up on King Arthur as an ideal. The perfect king. That idea survives to this day, and the idea of King Arthur has influenced ideas about what it means to be good, to be a gentleman, and what chivalry is about. It is possible that the character of King Arthur was based on a real person, but even if so, the whole idea has become romanticized and idealized. Mainly King Artur has had an effect on literature from within literature... people grasping on to the idea of a king who was truly good, who never abused his authority... who treated people with less power than himself still with respect. People like to have heroes that are better than themselves, who they can look up to and try to be like. In that respect, King Arthur stands as a beacon of hope to many. And if literature changed, and still changes, to give us more ideal heroes, then perhaps that means that humainity still hopes to perfect itself. :)