The old cliché "content is king" managed to become both old and a cliché by benefitting from an additional attribute: accuracy. The search engines themselves, despite being notoriously reluctant to share insights into their priorities, have consistently made it clear that they consider the content of your site the most influential attribute in keyphrase relevance and ranking. It's no joke: When it comes to SEO, content is the undisputed king.
The issue of the importance of content has multiple facets; don't make the mistake of thinking that it is enough to simply have large amounts of content. There are three aspects of content that greatly affect the amount of influence it has on a site's ranking: relevancy, recency, and quantity.
Relevancy is the top priority. If you want to rank well for the phrase "vintage mustang parts", then your page had better contain information about vintage mustang parts. A single mention of the keyphrase on...