Lets take Halo for instance. With Halo's massive universe and story driven narrative, it has the source material possible to make a good movie. However, the issue is that with many games that have a story strong enough to make a good movie, making a movie seems more like a step backward than forward. A Halo movie would basically be 2 hours of nonstop cutscenes. Especially, now that games look so good, theres no reason to adapt to the bigscreen because the bigscreen can't offer anything new to the franchise. And for some reason this makes movie execs think hey have to make subpar reboots of old games that focused on gameplay instead of story. See Mario, Tomb Raider, and World of Warcraft.