That's a good question. I guess the first question is, does your game run within a window? As we know, with most PC games, then will actually take over windows and don't always launch in just a separate window. So the only reason I could see this being difficult is that it opens over top everything else. I guess that you could still work with it, even though it does this, but this is just one of the areas I would view as being "tough".
However, as long as there is some sort of GUI that it interacts with, and as long as the application is open so that you could see what controls you are trying to attach to, I think you probably could. Although, since much of what is done in games is not stardard for Windows applications, it might be difficult to automate and may only respond to very low-level commands which are controlled by low-level commands (baed on co-ordinates), rather than the higher-level options we usually take advantage of when autoamting true windows apps.