What should I set my Asus vw266h to, to work properly with my 360

It’s been about a week since i got my asus vw266h and everythings fine, almost everything…I noticed that when i play the games on my 360 that everything looks kind of downgraded, and i’m wondering as to why that is. I’m using an hdmi cable, and granted things look a ton better than when i played on my standard tv, but i’m noticing that halo 3, and cod 2, specifically looks almost like a ps2 graphics, i could be being really picky but, like i can notice every single fault or line sketch. I’m not sure if i’m being too picky or what but it’s def noticeable.

some games like gears of war 2 look fine and particularly well with little noticeable lines etc., and hell my ssf4 looks pretty good too even if i set the 360 to 720p

Anybody with any tips?, to answer some questions you might ask:

yes I have went to the menu settings and changed things accordingly for best picture output on my monitor, but at the same time it still looks grainy, set the 360 to standard, ycpbr709, and 1080p. I also called asus and the guy on the phone kept cutting me off every time i tried to say something, when i finally asked him he pretty much told me " go to your 360 dashboard and set it up" after I already did it and told me he owns a ps3 and doesn’t have that problem. have also set it to “game mode” on my monitor.

I have also tried to set my monitor to the 4:3 settings, but the “4:3” setting in the menu won’t let me select it, the same is with the “screen format” on my 360 dashboard.

so is there any settings anybody is willing to share to help me out, or any other information regarding this matter?

Xbox should be on RGB with expanded color range. I use my Asus evo2k9 monitor on standard setting with Xbox and looks fine.