http://fossbytes.com/ubuntu-linux-is-the-most-popular-operat... https://duh6oa3w9hopv.cloudfront.net/uploads/pdfs/RightScale... etc.
The must be doing something right, but of course as quickly as they rose, they could loose the market equally quickly. I do see interesting directions, though: Ubuntu seems to be the default choice on OpenPOWER servers (at least for now) and it will likely be a strong contender; see e.g. https://www-03.ibm.com/press/us/en/pressrelease/47791.wss
One group that has certainly contributed and needs to be given credit is Debian!