Consider the mediums of books (A), movies (B), and video games (C). First, I'll make the (possibly old but I am not sure) observations about their inclusiveness.
Note that A does not include B, nor does B include A. Books lack moving images (though they may have stills) that define one of the most important aspects of the movie experience. However, movies cannot simulate the paced experience of reading books, where the reader chooses to go fast or slow, taking his time to appreciate the passages that are denser yet more rewarding, and skim past things for which he has no concern. He may also go back to earlier pages by flicks of the wrist, whereas "rewinding" just doesn't seem to do the same (an action which a moviewatcher in a theater actually cannot do, as opposed to a home owner).
Now, I will make the controversial claim that C includes both A and B. By that, I mean it is theoretically possible for any item in A or B to be presented in video-game form (without regard to whether such games will actually be published, of course).
Obviously, games uses movies. So it is theoretically possible to take any movie and include no other components except for maybe actions to pause, rewind to a previous section, fast-forward, insert bookmarks (ironic, no?), and bonus sections and call it a "game." It would be a boring game, but still a game. For books, it is even easier - just think any scrollable tutorial screen or one of the many books in "Elder Scrolls: Morrowind" (there is the additional caveat, of course, of the problem with the lack of a hand to read the book with and the "feel" for the book. But for now we can assume we are dealing with e-books or something...).
Now, obviously, I do not mean we should get rid of books and movies entirely! This brings us to the first point: bigger is not always better. This seems somewhat paradoxial, but it makes sense in considering that each storytelling medium is not defined by simply what it can do, but also societal and cultural values associated with it. Games (at least not now) are considered to be more along the lines of juvenile pursuit, and it seems weird to define the Encyclopedia Britannica as a game (although as we saw, we may definitely create a theoretical "game" which basically is the encyclopedia!). This reminds us of the all-important maxim:
In theory, theory and practice are the same. In practice, they aren't.
Jests aside, what constructive things can we learn? On the positive side, I think an immediate conclusion is that games are capable of so much more than we give them credit for (and what they are actually used for). Game designers should realize that they have an artistic medium of immense potential and be proud of it. They can (and should) look at the novels and films, their less-powerful but more venerable ancestors, and seek their wisdom. One specific example is writing: Yes, writing in games right now are definitely more eloquent than the "a Winner is you" generation of the 90's, but literary-wise, they are still at best even with the low-end of popular fiction writing. The classic novels have their charm for a reason, and games should learn from them. And I mean beyond long nouns and flamboyant adjectives. That does not define good writing. Of course, since writing is getting noticably better, I'll wait before making more comments.
On the negative side, I'll misquote Spiderman (or Spiderman II?) and say that "with great power comes great responsibility" (actually, this theme is as old as The Once and Future King, which is a great novel, by the way). I think one of the responsibilities of designers is to explore the medium for artistic rather than material gains, and take some responsibility on the increasing chunks their works are taking out of the children's time. I don't mean forcing educational value into games - geez, games were made to entertain - but at least feel guilty for doing video-game versions of many of the saturday-morning cartoons that most self-respecting teenagers will even look back and regret watching. Give the players innovation, give them some art. How about more ICO's and Katamari Damacy's? I don't know if the world really needs that many more Doom's and Quake's - of course, I don't mind Half-life or Counter-strike, both of which actively sought to introduce new things into the FPS genre.
I think I'll have more to say with this topic later, but my hands are tired.