There are some rumors in the industry that Google's algorithms have a positive bias towards WordPress powered content management systems. The truth is, that is not true. WordPress blogs and CMSs are designed to be very search engine friendly - which makes it easy for GoogleBot to consume the content. But there is no algorithm that says to rank this site/page higher because it is built in WordPress.
Google's John Mueller said this on Twitter. He said "WordPress is a great CMS & works well in search, but afaik our algorithms don't explicitly check for any particular CMS."
Here are the set of tweets:
So you can throw away that myth now.
Forum discussion at Twitter.