At a nice dinner in Geneva yesterday, a local customer pointed out that the most visited websites in the world do not use any of the "usual suspects" among the CMS vendors. Mediawiki is the open source engine behind Wikipedia, while Blogger and WordPress are popular blogging platforms. Among the top 30 sites today, the remaining 27 use systems that are propritary and home-grown.
Interestingly most CMS vendors consider themselves worthy of the classification "leading", and many other analysts frequently crown winners; "strong positives", place them in quadrants or use other horserace style approaches.
Some might argue that those 3 systems placed among the Top 30 are not actually web content management systems. That may be so, but they do enable effective web publishing. Perhaps you don't need a CMS to power your website after all?
I would argue that you should look at your own requirements and not too much at the labeling used by the vendor or open source project. If you are a high traffic site, I certainly recommend extensive testing and many reference visits before procuring a commercial CMS.
You can find detailed evaluations of all 3 systems in the Enterprise Social Software Report.