Joomla and Drupal are the other two popular ones, but if you are looking for customizability, I don't know why you wouldn't consider Wordpress as well. WP can be customized to run a wide variety of sites and I have personally seen it run many types of different sites.
Joomla is a really good CMS, ideal for creating more complicated sites with lots of customisation options, but also its a lot harder to use than WordPress, so there are trade-offs to consider.
Looking for an SEO-compatible CMS. I know wordpress has an SEO add-on... but would prefer static pages.