If you read my books you will find a common theme even though you are reading vastly different worlds and stories... what I call pauper to power, (others might all it rags to riches, but my characters don't always get rich). What they do is come from humble beginnings and work their way up to greatness. They may start out as a poor orphan, or a boy cleaning chamber pots, or a man with no possessions, not even his memory, but in the end, they will become embroiled in the great epic events of the world.
I certainly didn't make this up, or pioneer anything... it's just the way I like to write my stories. I feel that the reader (assuming he isn't the King of Atlantis, or something) can relate better to a protagonist who comes from humble beginnings. If you want other examples of books that use this, look at Lord of the Rings... ask yourself, who are Frodo, Sam, Merry and Pippen when they start their grand adventure? Or, who is Harry Potter, but a boy living in a cupboard under a stairway. Or Garian of The Belgariad, who grows up in the kitchen, and becomes the most important person in the world. There are countless examples of this mechanism, because it's a good one!
Not that this is the only way to write a good story, but I think that it helps you readers to connect with the hero, and it gives the hero something to achieve... greatness, from humble beginnings. The thing is, we all like to believe that we could achieve greatness, given the chance. That somewhere inside each and every one of us is someone just waiting for the right moment in time, the right circumstance, where we can become the hero. It is fun to ride along with other characters who achieve this greatness, and live vicariously through them, hoping the day comes when we too can show our mettle.