Sites that maintain a top ranking, they usually know the "secret" to following the algo and tiny changes are made that you wouldnt notice just by looking at it. Backlinks help, like I said
SEO is 80% of the deal. The other 20 percent comes from backlinks, relevant outbound links and so on.
Have you ever thought that some of the sites you speak about might be "owned" by a Google employee or someone that is key to their operation?