Going by those comparison shots it almost looks as if Double Helix was aware of what that filter would do and brightened up the games output to compensate.
Think about it like this- what sort of HDTV do most people have today ? That's right , probably a 300-500$ 32-40 inch LCD that has trouble displaying a nice contrast ratio , especially on the darker end. So having a filter that makes all those "invisible greys" (invisible to the widest TV audience) go to black doesn't actually do much to the image for that same typical TV owner.
On these forums you have many people that spent 800+ $ on a new TV in the last couple years and even on the LCD front , gimmicks with local dimming and LED backlights have allowed a more accurate color reproduction , so people on places such as neogaf , we can see all the differences between the normal and filtered image. Especially if you have a plasma TV.
Basically, the non filtered image just looks like the gamma is set a wee bit too high. Does the game have an internal adjustment for that ? If not, then turning the brightness on your TV down just a bit would probably remove that washed out look. Otherwise you can settle for the MS uber dark filter. Going by these screenshots I'd almost settle for that if I couldn't get a better image out of the 720p mode.
