Going to have to weigh in here in support of Halo. Yes, the basic plot is "Oh look, something not human, blast it!" but I'd love to see an origins story. Reading the books changes a lot of opinions on the characters, and tends to drop the "War is Hell/Big Damn Heroes" effect for "bad people in a bad place" story.
The Spartans were created to suppress an implied justified uprising outside of Earth's reach, the project literally kidnaps children and replaces them with copies that then die shortly after, the project's leader doesn't even think it's right. You even get the AIs (who are coded to be loyal - they have no choice in the matter) questioning the morality of the whole deal, as more and more children die in the making of the Spartans. Then, suddenly, the Covenant show up. They utterly destroy every human force they come up against, and the soldiers trained/engineered to be the best start coming to terms with the idea that they might not be good enough and it all might have been for nothing.
John-117 himself (Master Chief) is a much deeper character in the books - he can't stand being in space (he's afraid of being helpless), he's stupidly competitive (he hates to lose), he loses so many friends that you could easily diagnose him with separation anxiety (especially in regards to Cortana), and he hates the mythical image that the Spartan's have had built up around them (he comments that as Spartans officially can't die - they always are reported as M.I.A. - his friends can never truly rest).
Play the world dark, including its human parts, and play John right and you've got a deep sci-fi / military film that hinges on themes of morality and the lengths a power will go to in order to win a war. You'd alienate the majority of the fan base, but if you capture the feeling of the first book, it'd be worth it. Having seen District 9, Blomkamp would've been perfect for this - his ability to make us care about characters while being uncompromising about the danger they are in would've worked wonders.
Alas, if it does get made now, it will be about humanity triumphing over dirty alien scum. Probably with an Iraq war analogy thrown in somewhere. It won't even be ironically enjoyable like Starship Troopers (which I'm still convinced is one of the most unintentionally brilliant films ever).
Either that, or it'll be about tea-bagging.
