Bill can be a hero because the stranglehold Microsoft had on computer development is gone with the advent of the Web as the platform. No one is afraid of the big bad MS any more.
Everyone loves character arcs and comeback stories.
Creating new villains means there's room for the old villain to be rehabilitated. Even if neither of them have changed a lot as people over the last 10 years, the media perception becomes the reality.
However, as Jobs is so closely tied to the recent success of Apple, and Gates is still seen as Microsoft even though he hasn't been an employee for many years.