From a basic standpoint, both Killzone 2 and Gears 2 look about equal to me. Aside from the overblown and minor differences technically, I actually preferred the visual 'look' of Gears of War 2 better and actually to me its a better made game. Not in terms of fun, but looking at the design decisions and actual gameplay mechanics that Epic designed they seem to have a class which Killzone 2 does not match.
Tease.