>Weighted Attacks
>Enemy AI
Everything else is just icing on the cake. It's why I like Dragon's Dogma so much. It's pretty basic and not at all rocket science, but it feels like your attacks have something behind them, and this encompasses a lot of elements. From the animation of both you and your opponent, to the visual effects, the way you and your enemy stagger before and after an attack, the differential delay between types of attack, the camera angle, and so on. There's a lot at play that goes largely unnoticed in great action combat, and entirely unutilized in many.
In regards to Enemy AI, that can be explained with one simple quote
>It has to be fun to shoot at the enemy, as well as be shot at
In other words: make the enemy want to fucking kill you, and give them a fighting chance. That feeling of success comes from the innate fear of failure, and if there is very little or none at all, the game's combat will be memoryholed as soon as you finish it, if not before.