According to W3Techs Hugo is used to power approx. 0,026 pct. of the websites on this planet. That makes Hugo a an unrivalled no. 1 in the field in terms of usage.
The old leader of the pack, Jekyll, comes in second. A year ago Hugo generated half the number of websites, that Jekyll did. Today it’s twice. It seems, Jekyll has lost its throne.
At present the penetration of Hugo matches the penetration of well-known CMS’s like Ghost and Umbraco (at least in Denmark).
For further reading visit my article on the subject. It’s in danish, but Google translation might do the job.