Good Content is like peanut butter is to Jelly
As we all know, search engines are much cleverer now and, through what they call Symantec learning, know what makes up a great site from a not so good site and grades it accordingly. Many people try and fool the search engines by adding tons and tons of keywords, or keyword stuffing. A solid SEO company will be able to optimize the site for both search engines and humans resorting to what are called Black Hat techniques that will ultimately get your site blacklisted. Google has expanded its algorithm that catalogues and ranks sites to include Video and PDF files so this is all valid content if it's used correctly and the right way.
The more value you include in your sites/blogs/etc.....the greater chance that online success is right around the corner!
All the best,
Mike