Well, the first question is what kind of game it is. 2d? 3d? For the case of 2d, all you really can do is scale the output, unless you wanted to keep copies of the artwork for every resolution you wanted to support.
As far as I know, this is really easy to do in 3d, at least if you're using one of the prominent 3d apis(OpenGL for sure, not positive about the others
). In OpenGl, you feed the api world coordinates, and it handles the translation and drawing of them on it's own, no problem, and the output is the same no matter what the resolution, it just gets sharper.
If you're writing your own 3d engine, you can do pretty much the same thing by just not hard coding your perspective translations. Have those adaptable to whatever resolution you're running in, and you're good to go.
Jonathan, who really might not have any idea what he's talking about