I think Gears looks more chaotic than killzone 2, and they use lots of textures for creating that chaotic bumpy environment. Killzone 2 has more "organized" surroundings and everything is pretty much "squares" and "boxes". Since it looks more organized, people tend to think it has a more "calm" feeling to the eye, where they immediately jump the gun to "omg look at those textures they are amazing" where it's low textures with bump mapping. Just take a look at these images and you might get what i mean. They can be touched up or something, but that doesn't really help textures.
http://xbox360media.ign.com/xbox360/image/article/888/888964/gears-of-war-2-20080714001316563.jpg (this one is not touched up)
If you want touched up version:
http://images.gamersyde.com/gallery/public/8897/1560_0004.jpg
http://xbox360media.ign.com/xbox360/image/article/884/884154/gears-of-war-2-20080625074336814.jpg
http://img505.imageshack.us/img505/3555/156000045md2.jpg
In gears 2 it doesn't get more "organized" than this i think:
http://www.x-power.be/_gallery/Gears%20of%20War%202/gears-of-war-2-combustible-map-pack-03.jpg
KZ2
http://ps3media.ign.com/ps3/image/article/949/949161/killzone-2-20090129014112294.jpg
http://ps3media.ign.com/ps3/image/article/890/890010/killzone-2-20080715040152476.jpg
http://ps3media.ign.com/ps3/image/article/935/935547/killzone-2-20081203111746978.jpg
http://pici.se/pictures/GyyvdMdRW.jpg
If you look at how chaotic the worlds are, Gears wins it, especially with the organics and vegetation. I have yet to see a video or screen in Killzone where there's vegetation, and vegetation are on of the things that are harder to render. The textures in killzone just look "bland" imo. People forget that to create that actually ugly looking environment in gears, it takes graphics power.. Though Killzone 2 has lots more blur and apparently better AA, i still don't think it's superior from a technical standpoint, (exception of smoke maybe), but it is superior if you only look at the art direction. Most people will say gears of war 2 looks to have more detail but that killzone 2 looks more beautiful.
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