Recently, I had a discussion with a member of my gaming group concerning game systems and the game's narrative. My assertion was that the rules system will ultimately dictate the game's narrative. The assertion was influenced by a conversation at RPG Stack Exchange. The original poster asked:
Does choice of system impact the game as it's played by real people at the table, or is it all a matter of who the GM and Players are?
My answer is yes. My argument is as follows:
A role-playing game will have a narrative. The narrative begins the moment the rule book is opened and the players explore and begin fleshing out their characters. It is during character creation that the players begin building their character's backstory but more importantly, at least from the game's perspective, begin defining their character via the game's rules. This act of character creation is an agreement to play by the rules of the game.
The rules of the game define the framework for how the different entities of the game will interact and resolve conflict. Those entities include the environment, PCs, NPCs, Game Master, and players. By defining the framework, the baseline interaction is established.
Each group will clearly elaborate on that baseline: Will we talk in first person? Third person? Pantomime our actions? Play with props? etc.
Given that a plot requires conflict, and conflict represents two or more entities in opposition, then when it comes time to adjudicate conflict, the rules will be brought to bear.
Much like Chekhov's gun, if the rules, and thus the “first chapter” of the narrative, strongly emphasize one conflict resolution mechanic over another (i.e. physical combat over verbal dispute resolution), then the salient mechanic will be the more likely system used for resolving conflict.
In other words, if most of your rules are about melee combat maneuvers, then you can expect most of your story to involve melee combat maneuvers. After all the rules foreshadowed it and tacitly required it. Likewise, if you invest lots of your resources in a big shiny weapon and armor, then you will be inclined to use that weapon and armor.