..... Killzone2, No questions...
Lighting: Killzone 2 [Makes MGS4 look like a joke]
Character Models: Killzone2
Textures: Killzone 2
Scale: Killzone2's online alone beats MGS4 in this.
Particle affects: Killzone 2 [No contest here]
I'd like to add that Killzone2 is doing this without a HDD install. MGS4 has a 5GB install in the begining that's what... I can't remember... 7 mins??? Then a 2-3 min install between each act....
With Killzone2, you load up the stage in aroudn 25 seconds, then you just have a short freeze during a few slow portions on a stage. I'm talking 5 seconds or less. I think there are like 3 TOPS per level... I hardly even remember them.... can't remember a stage where I had this more than twice....
On a visual stand point, Killzone2 wins. On a tech stand point, Killzone2 decimates MGS4.
EDIT: The only place I could say MGS4 wins is facial animation. You could really see the emotion in their faces in that game.