@ Leo, I can't see dark/low contrast games very well and the issue gets progressively worse the longer I try to play them.

lets see it on a technical level shall we:

KZ2 :-
- x2 QAA
-native 720p rez

Halo3:-
-x0 AA
-native 630p rez

Now they've both gone for unique lighting systems, and both look good, but I've got to to say that the lighting in killzone just works allot better because it's more noticeable in the darker environments, although many would argue the opposite, but this of course is a subjective matter and as such is just my opinion, except for I've stated above.

perhaps you have something wrong with either your eye's or your TV, I had a similer thing happen to me and funny enough enough it was with Killzone 1, but I knew it was my tv, cuz I bought it on the cheap, now that I have my high quality  plasma HDtv the image is so much better, and while blacks are still blacks, their is no loss in image due to some fucked up internal gamma value which I could not change on my old tube TV.