I don’t like
Cyril. The name brings up the image of a wealthy middle aged or elderly man who is very much a stuffed shirt. I might use it as a name for a character in a story but never for a child.
I actually like
Kyrillos and
Kyriakos. I think these names are very usable in Greece or for someone who wishes to honor their Greek ethnicity.
I don’t like the female versions. They sound pretentious to me.