Its hard to pick the "best cms". There are a lot of CMS's out there. It really depends what you need - some CMS's are blogs, others are mambo. Some CMS's can do what you need them to do, and others can't. Lot of CMS's are designed for different uses for example Blogs only. Typo3 is very powerfull and has a lot of options. Only downside is that it takes a long time to learn but you can customize it a lot to fit your needs! Mambo is probably one of the most used CMS's for main websites and its not too bad. I've used it before and I like it.

Some CMS's don't require any HTML knowledge etc... and this could be best for people with no knowledge of HTML at all. But then, it might be limited.

In the end, a custom CMS coded to your needs is always the best, but isn't 100% necessary since there probably is 1 or more CMS's out there that can do what you need it to do.