Lucas originaly did number episode 4 the way he did to make it like you were coming in on the middle. But still he was looking at it as the 4th part of the story, even if he wasn't always sure he'd get around to making the prequels. And according to Lucas, he says that part of the reason he chose the ANH story to do first, was because it was the most straight forward and easiest to pull off considering the scope of the locations they would need to produce.
The whole saga together is Anakin's story. Luke is a big part of that story, but the overall story being told is Anakin's.
Luke does the right thing by throwing down his saber, but if it wasn't for Anakin, he would have fried like a port sausage.