The answer to your question is yes it is the correct path. But, you're looking at the wrong env variable.
PKG_CONFIG_PATH is the list of directories containing the metadata (*.pc) files, not the pkg-config binary itself. You installed pkg-config in the /opt or /usr/local hierarchy (can't tell from what you posted) and, I suspect, your old version is installed in the /usr hierarchy. Since it is likely that /usr/bin precedes /usr/local/bin/ or /opt/bin in your PATH variable, the configure script picks up the pkg-config binary in /usr/bin. As this is your old version, configure complains.
There are several options to deal with the problem. First and best, use your distro's package manager to upgrade pkg-config rather than install from source. For that matter use your package manager to install glib. Second, put /usr/local/bin or /opt/bin before /usr/bin in your PATH variable. Third, see if there is an option you can pass to the glib configure script to point to the version of pkg-config you want to use. Fourth, rebuild pkg-config-0.22 and pass --prefix=/usr to the configure script. This will overwrite your 0.16 binary with the 0.22 binary.
BTW, executing make check AFTER you install the package isn't much help. What if the test suite had failed? Now you have a broken package installed on your system. make check should be executed after make and BEFORE make install.