Obviously, some people didn't like it. Comics fans get upset when you put pants on a superheroine; turn their favorite superhero into Space Hitler and they'll lose their shit. Every time you do a story where a beloved character with 30 years of classic stories changes his good/evil affiliation, it's gonna ruffle some feathers. But here's the thing: The Ryan Reynolds version of Green Lantern isn't a beloved character. He doesn't have 30 years of classic stories. He has one so-so movie. That's the perfect setup for a sequel that subverts superhero tropes in ways movies haven't done yet. We've never seen an established superhero with one movie already under his belt turn bad. And no, X-Men 3 doesn't count, because A) the movie's name isn't Jean Grey and B) fuck you for bringing up X-Men 3.
So here's the pitch: The sequel takes place a few years after Green Lantern. Hal Jordan (Ryan Reynolds) is the universally loved and appreciated champion of the city that he saved from a giant monster in the first movie, kinda like Ghostbusters 2, but in reverse. But then the city gets attacked by another monster ... and Jordan fails. The city is wiped out. His girlfriend, his family, his precious bathroom cabinet equipped with all manner of hair products -- all gone.
All that's left from the entire city are two guys, a girl, and a pizza place.
That's when Jordan goes "Wait a minute, I have a magic ring that can do anything! I can bring the city back!" In his grief he tries to do that, but his bosses, the Guardians of the Universe, tell him that it is forbidden. Jordan replies "YOUR FACE is forbidden" (this line is non-negotiable) and murders the Guardians, absorbing all their power and thus the power of every Green Lantern in the galaxy. One of the Guardians manages to escape and gives the last Green Lantern ring to a new guy: John Stewart, or the Green Lantern you actually remember from the Justice League cartoon. You know, the guy so popular that when the Green Lantern movie came out, people wondered why Ryan Reynolds was playing a black guy.