From my experience, WordPress has been the most user friendly and seems to be the most popular. it may also be the most extended as-well. But you can probably make Drupal and Joomla sing the same song if you wanted to.
Wordpress is user frienly and has avaible tons of FREE plugins for whatever You need. It`s much more easy to on- page SEO, faster and flexible.
There are many cms out there like joomla, wordpress etc.. but wordpress is the best choice because its free, user friendly, have plugins and themes and much more just for free. But remember you must have to know how to control it because if you do anything wrong with seo then wordpress will be a nightmare for you.
Word press is the best CMS as large variety of themes are available and lot of plugins which would be helpful in doing seo, securiety, writing post, etc..I would rank word press, Joomla and then drupal respectively.
Vote for WP, it is easy to learn,open source,use phpmysql combination, more over attractive and reliable theme and have strong security.