People who have observed that Jobs benefitted from the inventions of others miss the point. Henry Ford didn't invent the automobile either, but he made it possible for everyday working people to own one.
That is the genius of Jobs. He was brilliant enoung to have a vision of a society where owning a PC would be like owning a toaster; at some point everyone would have one. True, the Xerox Parc featured an early graphic interface, but how many were sold? Jobs understood the just how valuable this interface was and envisioned a society where common household uses would be made simple through a relatively low cost personal computing devise. Same with the MP3.
It was Jobs' vision that set him apart. That and the attention to detail and the focus on quality