Ahh, three act screenwriting. You have to love these things.
however, as has been noted above, it does not translate properly to a game. Games are a newer medium than film, and are just now coming into their own as a narrative style, ("Half Life 2" and "Mass Effect" being notable for their driving stories) The thing is, these games are just that; stories. They have conflicts, resolutions, and new conflicts all leading to a finale. But the main thing the player sees is "Ok, how do I solve this one?"
In movies, the plot is the main driving force the viewer asks themselves "Ok what are THEY going to do about this?". It moves the show along. In games, it is the player that moves things they ask themselves "How am I going to deal with this?". Some of the best games are ones that allow for exploration while leading to an overreaching plot-line, things like Morrowind, in which the game presented you with an empty book, with a good plot-line to start out with. But how you finished the story was entirely up to you.
They give you a story, and tell you to run with it.
Morrowind barely even has an opening act. They start you on a ship, where you get to name yourself, then move you through character creation, and then put you into the world to do whatever, and be whatever. The conflicts the game presents are resolved by the player in the way they see fit, and then a new conflict arises.
However, I do agree that most good games have a structure to them. What that structure is, I do not yet know, hell... I doubt even the game designers themselves know yet. The thing about games is that they are so... open, the myraid ways of writing them so diverse, that a strict formula to making one just won't work. After all, try using the three act formula for making Tetris and it detracts from the game, but if you do not have a well made framework for a story driven game, even the best story will suck.
And never forget that game-play will define it all. Because the game-play is the vehicle that the story rides in.