Is there a reason for this? When I'm on windows 7 on my mbp the screen looks worse, seems everything is a little washed out. It's hard to describe but I enjoy looking at my screen when I'm on osx but on windows it is just lower quality.
Seriously though, a couple of guesses... is the resolution set to the screen's native setting in Windows Display Properties? Could it be a driver issue, as in driver is not installed or is incorrect? Did you download the driver disk from Apple? When you ran Boot Camp the first time you should have received a message that you will need to download drivers from Apple...