THE VILLAIN - The casting, except for Mark Strong/Sinestro and Michael Clarke Duncan as the voice of Kilowog was all wrong. Strong was the only actor who looked like he even gave a damn. If I were given the choice to write the movie I would have gotten rid of Parralax (who looked ridiculous) and Hammond who I, a heavy comic book reader between 1986-2000), had never even heard of. I would have started the movie out with the lantern corps coming back from a failed mission (possibly mentioning Parrallax here, therefore giving them a main villain for a sequel) and Sinestro being angry about the lack of power he had. He would then argue with Abin Sur over the creation of the yellow ring. Sinestro tricks the guardians into creating the ring, rebels against the Corps and mortally wounds Sur, who then crashes to Earth and seeks out Hal Jordan.
THE ORIGIN - Abin Sur gives the ring to Hal like always, when Hal questions what to do with it, Abin tells him that the ring will imbue him with the knowledge of the other Corpsmen who have owned it before. In one fell swoop we explain how Hal knows the oath, how his powers are supposed to work and how to manipulate them. More importantly, it conveys to him the importance of his new responsibility. They tried something similar in the movie that I don't think was explained enough. Hal is called to Oa for hands-on-training with Kilowog and Tomar Re, and admits to not being able to handle the pressure and responsibility. They tell him he is needed to help strengthen the corp in the wake of Sinestro's treachery.
- THE STORY - Hal struggles with the pressure, Carol Ferris could then serve a real point in helping him rebuild his confidence after he freaked out and crashed during a test flight at the beginning of the movie. Her love, and honoring the memory of his Father gives Hal something to fight for. Sinestro wants Abin Sur's ring, since Abin was one the most powerful Lanterns. He invades Earth and the entire third act could be a huge fight scene between the two, Battle: Los Angeles or Transformers style. Hal comes close to beating Sinestro but Sinestro's experience and hate fuels his power. At the end, Hal is willing to die to save Earth but the other corps members show up and Sinestro retreats. BOOM. Instant sequel where Sinestro builds his own corp in order to attack Oa.
Other nitpicks - the effects were terrible, as were the constructs Hal built. All of the creative (or in this case, non-creative) minds in Hollywood and they come up with him constructing a giant Matchbox car track to stop a falling helicopter and when he is being pulled into the sun, he conjures up two jets? Why not just create a super-fucking-awesome jetpack/booster on his back instead of being tethered to two jets? Ridiculous.
FINAL THOUGHTS - Lame effects, lame villains, lame casting. It should have been Green Lantern vs. Sinestro, instead of saving that for the sequel. Also, there is no real build up of Sinestro getting angry enough, or fed up enough to be putting on the yellow ring at the end of the movie. It made no sense other than to appeal to the fanboys.