By taking the concept of choice and mapping it onto spatial relativity, The Stanley Parable has created an extended metaphor that comments on the whole concept of choice in video games.
When we think of choices in games, the image we usually imagine is a clearly marked out situation with two or more responses represented by buttons or by on-screen options in the UI. The player then makes a choice by pressing the corresponding button or clicking on the preferred option. These choices then dictate how the plot of the game’s story will unfold. Think of the Mass Effect series in this regard or how it is wonderfully parodied in the walk and talk opening of Saints Row IV. These are generally moments different from the game’s standard style of play and need to be represented by their own system, one that is essentially separate from the rest of the game. It is as if the the characters have been brought into a sort of fugue state outside the normal game space, and in most cases, outside of the passage of time.
The Stanley Parable belongs to that collection of games based on genre minimalism that I’ve been calling the first person walker. While the game does have one click interactions that can open doors (in some cases) or push buttons (to little or no effect), most of the game is spent walking around corridors. Unlike other examples of the genre it doesn’t seek to minimalize a genre, only a certain aspect of it, by turning what was once an outside consideration into a physical aspect of the play space. What were once represented by a button appearing on the user interface now is literally represented as branching paths.