One of the things it seems I need to establish for my cynical professor is why choice is even a relevant element of storytelling in games. To paraphrase his point of view: choice in narrative doesn't really matter because most of the time people play through a game once and have no frame of reference for what it would be like had they made all the other choices anyway. From their perspective, it's still a linear narrative with a beginning, middle, and end.
Frankly I've struggled with trying to understand this myself, being that there have been plenty of totally linear games and narratives that I've enjoyed immensely. In fact, I tend away from a lot of games that involve branching narratives, not because I don't see the appeal but because it tends to deny consistency in character development.. or having character development at all. I like Commander Shepard of Mass Effect fame as much as the next guy, but at the same time she feels like a hollow vessel for the player rather than a real protagonist. 95% of her dialogue is questions. "What're you doing here?" "What can you tell me about your family?" "What can you tell me about the Geth?" "Any idea where they might be now?" "How many licks does it take to get to the center of one of those things, anyway?" There's clearly meant to be some significance to this character with the game centering on her to the point that the game's antagonists all obsess over the threat she poses, but at the same time because the developers don't want to take any control over her actions and even her thoughts away from the player she undergoes absolutely no growth and exhibits almost no personality traits outside what attitude the player chooses for her at any given time. This seems contradictory, but in an odd way the player-controlled character in this instance is actually more of an automaton than the non-player characters. This makes it really difficult for me to relate to her, see her alleged significance, or even understand what themes the game is supposed to be centering her story on. In theory the player really doesn't care about this, simply perceiving Shepard to be themselves and filling in all the blanks left by the script, but the storytelling methods of Mass Effect are so explicit there's almost no room for imagination to speak of.