9. Cause and Effect
This one's really a given, when you consider how much of a fuss people kicked up at the end of Mass Effect 3, when the choices we had made through the previous two games turned out to amount to very little, when the final scene in the game presented us with a reductive, simplistic choice of picking a colour and hoping for the best. Branching narratives can definitely get messy in the wrong hands - just look at something as promising and ultimately disappointing as Fahrenheit - but when they're executed well, they are extremely rewarding, as we can draw the line from A-to-B over the course of 10 or 20 hours and deduce that what we did had a significant impact on how things played out. Many games, like Mass Effect, have tackled this in a superficial way, but after the uproar following the last game's climax, it's time to reward gamers who were so let down and actually give them the cause and effect they crave. Though one can imagine something like this being an absolute headache to develop and code, that doesn't mean they should just take the lazy path of least resistance. After ME3, BioWare have something to prove to us, so hopefully this is the area above all that they will focus on refining, even perfecting.