I think a movie is completely possible and pretty easy to do here, and to appeal to a large mainstream audience. Personally, I would do this..
Chunk the movie up into 3 or 4 movies.
Movie 1: Opening credits start in with the close up shot of the TV showing a commercial for the Vault Tec and other products and pull the camera back to see a family sitting in the den with a 1950's look and feel like you see in the game and camera pulls out of the window and up through the neighborhood and into the sky back until you see a shot of a single missile flying through the air, then hundreds more a few seconds later. Then the camera dives down along with the missile and you see the great explosion. Then back to that TV, and as the camera is pulling outward again you have the typical "War....war never changes.." speech as we see the whole neighborhood all rubble.
This movie would focus on the typical vault dweller and the water chip aspect o the first game. To help with the typical "leveling up" of the game I would have the pip-boy be hard-wired into the brain. As in, they choose this guy because of his physicality and teach him new skills by him readin literature, then his pip-boy etches it into his brain. Totally a montage scene. And then hes let out into the wasteland and finds the water chip and the masters army like in the first game. In the conclusion he would come back to the vault to be declared a hero then before entering the overseer doesn't let him in because he's been changed by the outside world. Just like the first game. Then he walks away to find a new life.
End credits scene where we see him sign up for a caravan company on its way to Las Vegas!
Movie 2: Pulll the story from the New Vegas storyline because Fallout 3 wouldn't make a good transition. So opening scene in
this movie would be the some people digging a grave and have our main hero getting buried. But he's rescued by the securitron. So basically you have a badass character that's all levelled up and "experienced" but the bullet makes him forgot his past life. Then throughout this movie it's the journey to New Vegas and the fractions all vying for the attention of this badass guy who crawled out of a grave to find Benny. Then near the end of the movie have the battle of Hoover Dam looing and where his loyalties are going to lie.
Movie : The first half would deal with the mounting tensions towards the battle of Hoover Dam, and personally I would see him helping Mr Houses storyline, youll see why later. And then in a lengthy battel scene then have the whole hoover dam fight. In the end, Mr house takes over vegas and defeats the legion, and the courier doesn't feel right about staying there so he leaves on a journey to find out about his past.
I think those would be a good frame for the movie to be in, and for the love of god no love story. And have it look like Book of Eli, but with some references to a silly nature, much like the original games. Like a scene where we see anative american looking guy being dragged away claiming he's trying to help his tribe or something (from fallout 2).
Then after the credits or whatever of the third movie, you have our main guy start work on project purity, or allude to it. Then his son will be the next awesome main character.