It's a shame the manufacturers are too short sighted to make tv's that allow for seperate settings for each input. It's a basic requirement, but very few CRT tv's let you do it.
You're right in saying that brightness settings will differ depending on whether you calibrate in a dark or a light room. The Video Essentials dvd advises that you should always calibrate brightness in the same light conditions that you intend to watch films in. The problems come when you find the settings that suit dvd's don't suit other sources or inputs. It's a common problem, and there's often no convenient way around it, other than to constantly change settings each time you play games.
The only way you might get around it is if your dvd player has it's own controls for contrast, brightness etc, and they allow for quite wide ranging changes. That way you could set the tv to whatever looks good for games, and then lower the dvd's onboard controls until the dvd settings are correct, but the chances are the dvd player won't allow contrast to go low enough to compensate for the tv's brighter settings.
There's a link
here to a thread with some pointers to sharpness settings.
If any manufacturers are reading this, then please............GIVE US TV'S THAT ALLOW FOR SEPERATE SETTINGS ON EACH INPUT.