I personally believe the fundamental reason why the video game medium has not been able to establish itself as a unique medium through which to tell stories with its own merits and demerits, is because developers aiming to tell a story through a game approach it the wrong way. Almost all developers will try to put the player into the role of the main character, which from a storytelling standpoint means the player and the main character should be the same person. However, they are almost always not. The main character almost always has a distinct personality, and far too often makes decision on his or her own which may or may not conflict with the decision the player would have made. In other words, games give players a role that should have a huge influence over the events in the game, yet rarely actually allow the player to manipulate the story. The fundamental problem, therefore, is that games present unchanging (or almost unchainging) narratives from the perspective of the player.
This means that to actually take full advantage of the medium in terms of storytelling, a game would have to tell the story from a perspective with little or no influence. This makes sense since in other media the reader/viewer has little or no influence over the events of the story. This kind of approach could allow freedom in what the player observes, maybe manipulating time so as to get a look at all the events in the story (since you can do that with books and with some exceptions movies), and generally observe a story without having to work hard just to move further into the story. This way, instead of getting distracted from the story by the gameplay element, the player can actually enjoy a new level of storytelling only made possible through the gamplay.
That's just my take though. And of course developers wouldn't do this because many of them just want to create mindless fun that fools the few who want to actually make a story into thinking they need to follow the same rules of offering challenging, distracting gameplay. I find it unfortunate because I would really want to see a story where for the first time you're freed from the fixed viewpoint that other media offer.
