That's because it would take a genius stoned on crack to figure out a plausible way to make a good Mario film.
Fallout, on the other hand, is excellent film material. The real challenge would obviously be choosing the story. Would it be large scale focusing on the wasteland as a whole, or would it focus on one person's journey through the wastes. If you think about it, the setting in Fallout 3 is sort of similar to 'The Road', and the story of a Vault Dweller leaving the vault and having to survive in this living hell could make an excellent story, aslong as it was told with a Coen/Tarantino tone of darkness to it.
For every decent video game film (I saw Silent Hill and found it to be very true to the material of the game, a rarity) there is a HEAP of crappy titles. In recent memory Doom, Max Payne, Dungeon Siege, dead or alive, Alone in the dark, Resident Evil: Extinction... It is a proven rare thing for director to adapt games into good movies.
Now, fallout... it has the basic elements of a film, sure. A reluctant hero sent in to the wasteland, a post apocalyptic world filled with danger, guns, six, and a journey. But those are just the barebones of what made fallout great. Witty dialogue,pop cultural references, cheeky jokes/humor, overdone gore/death and more... Case in point, a director/producer has a TON of opportunities to mess up this film and would more likely end up as barebones film.
Like the doom movie: "Ok, hell invades a mars station and demons/hell pours thru the portal there. Demons? Hmm, that is to touchy to the religious crowd... lets make them Mutants instead! Perfect! Heck lets throw a 1 min FPS moment in the movie to make players of the game happy!"
Btw, they are making "The Road" into a movie... filmed in nearby where i live in Pittsburg. I read the book and found it a sad tale and struggle for a father and his son (now it is going to be a daughter instead, in the movie). It is one thing to cut portions of a written story into a flim, it is done all the time. Lord of the Rings was a landmark in adaptation of a book to film in a long chain of successes. Peter was passionate about the books and had a vision for the film with a expectional cast, crew and art department. All the right players, at the right time. Could this happen for fallout?
And the comments lets get Peter Jackson to make the film!!111... Do you know how busy he is? Do you think he is even aware of this game? You do know he picks what HE wants to direct/produce... he is supposedly helping with Halo but that may now be in development hell.
Edit: Now graphic novels are being bought up to be made into films... Anime is starting up too with Dragonball, Akira, cowboy bebop... Hollywood is looking everywhere for fresh movies to make.