Another point is that enviroment effects combat. Height differences, light and shadow, weather and the movement speed and distance to the target all effect the chance to hit. Enemies can act as groups and even react on your visible strenght. Special items like combat drugs, night googles and flashbang and EMP granades offer you additional possibilities for tactical decision. But the most important point may be the more direct controls, which offer pixel perfect movement and collision (while games like Diablo 2 use small squares), egoshooter-like wall sliding and the possibility to make side steps!