No one knows what kind of TV you have, for starters.
I know that on Sharp TVs, the Gamma isn't the same in Game mode and you're locked into an Expanded Color Gamut if you're using a Quattron set.
Actually, I think on a majority of TVs, usually color processing and Gamma is affected somewhat in Game mode, even if you use identical settings.
Game mode, just about all the time, handles motion WORSE than any other mode when using an LCD because all processing is turned off. It will be a bit more blurry, but the action on the screen will move faster and input lag will be reduced dramatically. (Input lag is the amount of time it takes from your input of a command or button on a controller to when the result shows on the screen.)