My Sony Bravia 56' TV dims/darkens when parts of video games become dark. This is frustrating as when a game is supposed to be dark the TV makes it even darker making it impossible to see, can anyone help with this?

My Sony Bravia (42") has controls that can set the brightness for all of the inputs, or, optionally, just for one particular input. You might have the input where you connect the video games, set to be dimmer than the others. Have you tried changing the brightness and contrast? I assume you have, but I'd like to confirm that.