Green Lantern committed the cardinal sin of action movies by being boring. The pacing of the story just seemed to limp along from one scene to the next with no real motivation. Also limp is Hal Jordan (Ryan Reynolds) as he is probably the worst superhero ever portrayed on screen.
Some of My Problems With the Film:
Ferris Aircraft is demonstrating their new drone aircraft in hopes of winning a military contract. Carol and Hal are chosen to go up against these unmanned craft. This makes no sense as both Carol and Hal are employees of Ferris Aircraft so the Airforce wouldn't be all that impressed if they lost to the drones. The test would be drones against either Airforce supplied pilots or from some other independent agency.
Hal Jordan wins the "Douchebag Award" during this aircraft demonstration by using Carol as bait so he can take out the drones. He does this by abandoning her so that she get's shot down allowing him to come up behind the drones (note: this tactic also fails). So in real combat he would have been setting up his wingman to die. Then Hal loses his plane because he has a flashback of his father dying while he's in a flat spin. Heroes with daddy issues, who can get enough of those?
This movie also did about as much research on how the Green Lantern rings work as the Superfriends did. Hal at one point uses the ring to create a flamethrower that generates actual flames. You know, of the orange and yellow variety. Later he uses the ring to create an anti-aircraft that fires I'm guessing real bullets because the barrels eject yellow fiery muzzle flashes.
Hal also has the worst reaction time of any superhero I've seen. At the Ferris Aircraft party a helicopter's tail rotor is damaged which causes it to spin out of control. Hal sees this but we are forced to watch the helicopter spin and bob through the air, crash to the ground, skid and bump through the party goers until Hal finally uses the ring to create a Hot wheels construct to move the crashing copter out of harms way. What was Hal doing during all the chaos? Looking for a phone booth so he could change into his costume? All it would have taken is one classic Hal Jordan giant green hand to pluck it out of the air and set it down somewhere safely.
Those of you who thought that Anakin and Amidala in the Star Wars prequels had the worst romantic chemistry in cinema history will have to adjust their views as Hal and Carol fizzle in every scene they share.
Fighting a giant cloud as your films final act didn't work in Fantastic Four: Rise of the Silver Surfer and it didn't work here.
And of course the design of his costume and the power battery sucked.
On the Positive Side:
Mark Strong as Sinestro. He was excellent.

