I somehow managed to pull off a 40-hit combo the other day in Batman: Arkham Asylum. It was glorious! It was also easy... in comparison to the combo systems of other games.
I'm usually not a fan of combo systems. That's because I have to remember well over a dozen button combinations... XXY, XXXA, X+Y then A while rolling the thumbstick from down to forward, etc.
In Arkham, one can pull off a fun and impressive combo with nothing more than well-timed presses of X and Y. If an enemy has a knife, you'll need B. If an enemy has shock baton, you'll need to double-tap A. With two-to- four buttons, I can put Jet Li to shame.
There are a few other commands that can be given: A+X to throw, Y+B to cripple, LT for a batarang. But they're unnecessary, and combat is a blast without them.
Arkham achieves this through context-sensitivity. One button activates one of dozen animations depending on how the player-character is oriented in relation to enemies and timing. Even the special moves, like throw and cripple, vary in effect or animation.
I guess, if I see a lesson in Arkham Asylum's combat system, it's this: the dynamics of combat don't all have to be controlled by the player. You don't want to cut the player out entirely or fake participation. But complex combat systems don't have to mean complex controls or instructions.