It depends what you want to do and how you define "CMS", different people have very different ideas.
Like if you just want a blog, Wordpress is ideal and can be extended to do more with plugins (though these can introduce performance and security issues).
If you need something more fully featured, with static/dynamic pages, articles, member systems and so on there are full concept CMS's out there.
If you are a developer or have technical expertise, Drupal is decent, though it has its own issues; its big, bloaty, doesn't perform well on normal servers (it has the Magento effect).
Joomla has a better entry level technically, but its known to be buggy, have security issues and performance issues, it too has its level of bloat.
Honestly I'm not a fan of either but that's my personal preference I suppose. Drupal and Joomla are popular though and are used for sites with big scope; but you find they are more developer focused solutions rather than end user focused solutions.
You then have CodeIgnitor and ExpressionEngine (the former open source, the latter is the commercial equivalent), of the commercial CMS's I've listed so far Expression Engine is the better of the solutions. Code Ignitor I've never been happy with and I've always felt as though its probably more of a "try this, then buy this" kind of scenario.
I would say Expression Engine is a nice solution though, it has a decent structure, has the feature scope for most websites, its not too bad to extend, I'm not that mad on the template system though. But it has a end user benefit in that its quite easy to get up and running with it.
We have our own CMS that we have built, internally to power client websites. We've recently made that CMS public, its a "Publishing Suite" type affair that's aimed at brochure websites, article sites, review sites and the likes (where content and publishing are required). It has member features and a forum but they take less prominence. Of course I am bias as my solution was built to suit my needs and my programming style, but those who have used it have liked it. It is designed to install easily and just work for anyone with no technical expertise but programmed in such a way that developers can extend it and re-engineer it easily.
Rapid prototyping was a big decision with it, as we needed to do that ourselves.
Some links for you to check out:
See my sig link for what I use to power most of my websites, for obvious reasons
http://expressionengine.com/ < my preference if I'm not using VUE