There are hundreds of Content Management System(CMS) and Web Content Management Systems(WCMS). The choices reduce when you decide on the segment you are interested in, such as E-commerce, Marketing, etc
I want to build a shop online
If it's purely a shop then go for a CMS that is E-commerce orientated such as Shopify, Prestashop or Magento. These are built from the ground up as web-based shops. The often have the ability to display normal pages as well.
I want to build a Marketing Website
In this segment, there is a considerable choice, most people that want to build a marketing website choose WordPress which is a widely used and very popular option. As a web developer, I find WP to be a challenge where page layout is concerned. My personal choice and one I recommend most often for the segment is Concrete5, It has a much more logical WYSIWIG approach which makes page building far easier. The whole customer experience, I find, is far more enjoyable and pleasant. This is gauged by the low number of support calls I get from Concrete5 clients when compared with CMS's.
The other deciding factor is the platform you are using. Here the main choices are Linux or Windows. Of course if this your only website and you are buying hosting as well then I would recommend Linux. We have a hosting option for Concrete5 on Linux, see the Hosting Page for more detail.