However, many games have different requirements depending on what they support. So one game file format would not work.

What if I wanted/needed my model to have more than two UV maps? Perhaps I needed one for the diffuse channel, one for the normal map and one for the bump map? It is not likely, but it can happen. If the game file format does not support it, then I cannot do what I need.

FBX is a good, all-around file format that can be used for a variety of applications and a variety of reasons. What needs to happen is the developers that want to use FBX simply need to make sure it imports what they want correctly and then to instruct their users what to avoid, if anything, when exporting/importing via FBX.