Let's be honest here, given the LOOOONG history of video game movies, that is highly unlikely.
This is the main reason, in my opinion. Not everyone played as the default character, nor did everyone play the game the same. This isn't some linear game, with a specific lead character. This game has way too many options, both in character customization, and in character interaction, that the movie has no "definitive" story to base itself on.
True but everyone has seen the trailers and comercials so they get what Sheppard looks like and in my opinnion that perfect look is Fox.
Sure, the default Sheppard. But, I didn't play as default, nor did any of my friends. And we all acted differently in the game, as well. Will the movie have Sheppard as more "Renegade" or "Paragon" in his/her actions? So many different ways that people could have done things, how do you specify which is "correct" for the movie storyline? What type of character will they be? What armor and weapons will they use? This isn't a Gears of War movie, where we have specific characters going through a specific, predetermined story, with premade cutscenes and dialogue.
