WordPress, Joomla and Drupal are the major Content Management Platform that are almost ruling the internet. In that 60-75% websites are build with WordPress, 10-15 with Joomla and around 7-9% with Drupal, so 90% of the website world is depends on these three. It is because of the audience focus, interest, ease of use, edit, add themes, plugins etc, default blog friendly etc.,
In my experience many S E O(Search Engine Optimization) experts says, WordPress is the most easiest and finest C M S platform to boost your S E O with its incredible number of plugins that are easy to add meta tags, description, on page optimization, visitor tracking etc.,
In fact, there is no major rule to use C M S(Content Management System) to boost S E O, we know it's all about better on page optimization and proper S E O methods. But for user usability and ease of access makes the difference.