Green Lantern's review scores are a little artificially deflated, I think. There's nothing really wrong with it other than dangerous levels of Ryan Reynolds. It's just that it's a superhero movie trailing at the end of a long line of superhero movies. Hero is introduced, establishes he's sort of a schmuck, gets superpowers, gets exposition, fucks off. Villain gets superpowers, is a dick in public, hero stops him. Media coverage, hero gets girl, hero screws the fuck up, girl pep talks hero, hero saves day. Credits, sequel hook, more credits. Lather, rinse and fucking repeat.
The thing about Green Lantern is that he's a pretty strained concept for a superhero from a dramatic standpoint to start with. Hey wouldn't it be great if Superman wasn't just invulnerable and infinitely strong but could also conjure anything he wanted out of thin air at any time? The movie tries to inject a little weakness with some bullshit about blah blah blah fear but when Reynolds is supposed to be freaking out the best he can muster is looking slightly less douchey for a few moments. I have to admit the writing's a little weak at other times too, like the bit where it's revealed that the ring just gave Hal instant knowledge of everything in the universe ever and then two sentences later he's asking poor Mr. Fishhead Exposition Guy to re-explain everything that was established in the opening narration. Overall it's just a big dumb familiar waste of time that looks pretty good up on the big 3D screen. There are much better things you can be doing with two hours but if you're going to waste them on something, you can easily get through this one without wanting to hack off one of your limbs to get away.