Halo seems like the sort of property that'd already have a major motion picture under its belt. The games have been a huge success for nearly 15 years, and with Hollywood as it is today, it's surprising that films aren't already being made. For the longest time, live-action Halo projects had a hard time getting off the ground, and while there's no big-budget film just yet, smaller projects like Halo: Forward Unto Dawn have finally managed to get the ball rolling.
The next step towards Halo in Hollywood is the live-action series Halo: Nightfall. It's an ambitious project: Nightfall was designed from the beginning to act as a bridge between the Halo games and future projects. It's an interesting idea, especially since Microsoft isn't charging fans to watch the show...but just because the show is free doesn't excuse Nightfall of the mistakes that it makes.