Brief:
There really isn't a single CMS that outshines all the rest. You should carefully tailor your choice of CMS's based on the site specification.

Not so brief:
The underlying assumption here is that ongoing maintenance of a modern website is (or even can be) a non-techical task. This is unfortunately unrealistic. As an example consider the needs of a "simple" single user blog.

Any blogging CMS worthy of the name should provide a simple interface for adding, editing and deleting content. It should also provide a simple interface for choosing which content is displayed on the site and most do.

Well and good, but what about related content? Should a user be shown a list of related links when the view a blog post? How is "related" content defined? Is this limited to content on the site or should off-site links be included?
Should this list be sorted by date, relevancy, popularity?
What about rich text formatting or pasting content from MS Word?

Most blogs also have some mechanism for accepting and displaying reader comments and just about every CMS I've ever come across has some method of handling this. But again we run into problems. Spam is a real issue and spammers have taken to using mechanical turk and other methods to get real live people to post spam for them. This approach completely bypasses captcha and even the best automated anti-spam services (mollum as an example) can't catch all of this, so now you've got to include manual comment moderation (which is a shitload of work on a heavily commented site) into the mix.

Generally blogs also have RSS feeds and social media links. Most CMS's handle these fairly well without a lot of tinkering but it can get interesting if you (for example) want to segregate your content into multiple feeds based on subject matter or whatever.

So even with a "simple" site the end user has a lot of potentially very technical decisions to make regarding how content is displayed, who can see what, who can comment, how comments are moderated, and what (if any) content is syndicated. Note this doesn't even get into SEO or analytics.

The point I'm getting at here is even simple websites can be miserably complicated little beasts and unfortunately only so much of this complexity can be abstracted before you start running into issues where the available feature set isn't a good fit for some/most/any websites.

With that said each CMS I've studied attempts to solve some subset of the problems associated with creating and maintaining a website. Which subset is tackled varies wildly from CMS to CMS.

For example Wordpress does an excellent job of solving most of the problems associated with implementing and maintaining a blog. I wouldn't care to implement a company intranet portal with it though.

Drupal is incredibly flexible, with plugins available for just about any feature set you'd care to implement. It is brilliant when a site has a complicated or fiddly feature set, but can be intimidating to end users due to the steep learning curve involved. As such it's frequently overkill for truly simple websites.

Various other CMS's have their own core competencies and tend to shine in the situations they where developed to work well for.

If you're looking for something to pattern off of my suggestion would be to first figure out which CMS you would reimplement your site in if you had the option and then go from there.

Edit - Full disclosure: I'm a contributing developer for several Drupal modules.