Speaking with Game Informer, Bioware Executive Producer Casey Hudson, man in charge of all things Mass Effect, a man many of you might want to kill after the changes in Mass Effect 2, the man who has ruined all other men for you…. Sorry… an Office reference slipped in there.
Anyways, Hudson has said to Game Informer of Mass Effect 3's Story, Action, and RPG game modes:
You have to make a game with a certain design before you realize that there are different player types. One of the surprising pieces of feedback was for some player, it's not that they don't like the story. They love story. In fact, the story is so important to them that they feel the story choices are intimidating.
So all these setting do is that they set some of the options on the option screen before you've played it and know what those options mean. Once you get in and start playing, you can change things.
If you choose Story Mode, Mass Effect 3 will automatically dumb down the action sequences. If you choose Action Mode, the game will choose dialog automatically. RPG Mode? Well, you can guess where that takes the player.
[Source]
