I have heard this a number of times from Arch Fans, but I think I disagree. While I have referenced their wonderful Wiki often for "cook book" style answers (like how to fix URXVT+Tmux interactions), I do not view it the same as good documentation. I would also not really call it "comprehensive". To me, good documentation is as comprehensive as possible of the entire subject, and not just a "how to" on configuring it to look or behave like another user's installation.
Compare the Arch wiki to The OpenBSD FAQ [1], the FreeBSD Handbook [2], or good man pages [3]. The FAQ and Handbook have thousands of pages of comprehensive documentation and examples. A well written man page should be capable of answering most of your questions and allowing you to determine what actions you want to take.
I prefer the comprehensive documentation, or thorough man pages. Although, I definitely appreciate the usefulness of the "cook book" style Arch wiki.
[1] http://www.openbsd.org/faq/ [2] https://www.freebsd.org/doc/handbook/ [3] http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man4/...