I really like your take on that Christine. I think that there are good churches in nearly every decent sized town/city. When I mean "good," I mean a church that is theologically sound. It might not mean that you really like the worship style, the format of small groups, the size of the church, etc., but I do think that in most places, there is a quality church available. I'm basing this only off my own experience and the experience of my friends who moved after graduation, so my perspective may be limited.
I think looking at a move as a "calling" is great. In a secular college, our ministry target was usually pretty clear: peers in our majors, neighbors in our dorms, friends in extra-curricular activities, etc. After graduation, it seems to get a little foggier (or at least it did for me) as to who we're supposed to minister to. So in addition to asking "is this a place I could serve others?," I think we should ask "Is this a place where I could serve WITH others?" I think usually, we can be more effective witnesses and more energized ministers of the gospel if we are in good fellowship. Sometimes a church might not have a ministry specifically for the "just out of school and just married" crowd, but I don't think a lack of a church with a specific ministry for your demographic is a good reason to not move somewhere. To fill in this gap, some parachurch organizations which have fellowship groups in larger metro areas around the US. These groups are designed to help young graduates and young couples sort out what their role as witnesses is as they enter the working world.
I think a great church or a unique opportunity to serve could be a "tipping point" factor in deciding whether/where to move, but I'm not sure if it should be a major factor. Since God is at work everywhere, right?
I would look at a situation like that differently.
Rather than looking at the locale as a place that can serve my needs, I look at things as significant as taking a new job or moving to a new neighbourhood as a calling. Am I called to this place - which is really asking, am I called to these people? Whether or not there is a good school or "cultural amenities," I would first ask if this is where God wants to use me. A place that doesn't serve my needs might be exactly where I should go. In fact, a "bad" church might be just where God wants me to serve, and it'd likely be a place I would grow in ways that I could have never anticipated.
God's wisdom is infinitely greater than ours.