Depending on your ancestor's background, you may be able to narrow down or eliminate some of those churches. Old St. Mary's was a traditionally German church, and St. Patrick's members were mainly Irish, if I remember correctly.

There are a few books on Catholic Churches in Detroit that may help you. You can also Google the name of the church and see what comes up. The Archdiocese of Detroit's website also has a listing and brief description of each church and its ethnic affiliation, if applicable.