What part of the Halo trilogy would work best as a movie?

all three would make a trilogy better than pirates of the caribbean

The first would be brilliant as a movie. Although... that's only if they follow the storyline unlike in most films that share game titles *mutters darkly*. If they then decide to continue I spose the 2nd would be a good film too, not sure about the 3rd, I haven't even got the system to play it ^^;