I admit the first preview left me cold, but I've been a GL fan for a while now (starting during the Kyle Rayner era and all the way up to the Geoff Johns era) and hope this pans out. There's a multitude of villains and storylines, especially recently, to pull from to create a strong series and story arc for Hal.
The first movie - Hector Hammond and introduces Sinestro.
The second movie- Sinestro goes evil and gets a yellow power ring; maybe even introduce the Manhunters, hinting at the Guardians' shady past
Third movie - Mogul destroys Coast City, leading to Hal's battle with the Guardians; perhaps he's redeemed by a Star Sapphired Carol Ferris or he becomes Parallax; Black Hand could exploit all the death in Coast City
Fourth Movie - all out Sinestro Corps War/Blackest Night
Wouldn't even take much planning, as Sinestro, Star Sapphire and Black Hand could hint at the greater emotional spectrum over several movies without it feeling shoe-horned in.