As a huge openbsd aficionado I don't think openbsd is more secure than any other operating system, or more correctly speaking, I think openbsd definition of security is different than most peoples definition of security. If anything, by most peoples definition of security openbsd may be less secure.

Most peoples definition of security is to have improved access control such that unauthorized access cannot happen. The openbsd definition of security is closer to "build it correctly so that it operates correctly". openbsd access control is actually fairly limited and rudimentary.