Most games these days include narrative of some shape or form. But simply attaching narrative to a game is the least efficient way to leverage the power of storytelling! A good game meshes narrative with the gameplay features and mechanics themselves. The narrative is no longer something players simple expereince between sessions of gameplay; rather, the narrative is utilized to inform the player of the mechanics themselves, deepen the purpose of the actions the player is performing, or enahnce any other aspect of the game itself. Ultimately, narrative is not something you just add to a game; it is a tool used to expand upon and deepen the other aspects of the product itself.
In Portal, the player is simply dropped in a world with no clear reason as to what is going on or why. GLaDOS, the only narrator the player encounters in the game, spurs the player on through her testing facility. Why does this facility exist? What exactly is going on in this world? Why are you being forced to "think with portals"?
The narrative of the game doesn't outright answer these questions, but it DOES provide suggestions. Without spoiling any particular aspect of the game, as the player progresses through the trials afforded to her by GLaDOS in the name of "science" the player begins to learn that something is extremely wrong. There seem to be no other humans... and the player wasn't the only subject to enter the Aperture Science testing facility.
In the end, the narrative in Portal does more than tack a story on to an almost gimicky mechanic. It expands on that mechanic, explains the player's (and the avatar's) objectives and goals, and deepens the environment the player must traverse. Narrative is not simply attached to the game; it inundates the game and enhances the experience of its players.
Life is Strange
Life is Strange focuses primarily on it's main mechanic of controlling time. However, there wasn't a random story that was simply slapped over this but, rather, a unique, coming of age tale that suits the control. The narrative enhances the mechanic and vice versa, creating an interesting play experience as well as a new way for players to make choices and have a different kind of sense of agency..