I've covered horror and FPS, so now let's take a look at mechanics and narrative in RPGs.
Roleplaying games typically work a lot harder to construct a complex narrative than other video game genres. They also typically tend to focus a lot on the player's choices and how they affect the characters or story. But there's a balance here: giving the player too much freedom weakens the narrative, while not giving them enough makes a game that's supposedly about freedom and choice feel pretty restrictive.
Personally, I have a lot of problems with how many big RPGs handle choice - I find that they simultaneously offer too much and too little freedom. The very principle at the core of the RPG genre is the root of almost every issue.
