What about contrast ratio?
Contrast ratio is a misleading term...
It is the difference between extra bright sections and dark or black sections of the picture...
What manufacturers use is usually a dynamic number which means nothing really, just that they use a 100% white screen for white, and a completely black screen for black...
You need to see the video pictures in the store with a video signal that you know...
One that contains lost of black, lots of whites, and very good range of grays...
Try a movie which you know has this, like Dark Knight, or Batman Begins, T2 is also good...