I liked it, but then again I'm probably the biggest GL fan on OCR. Wasn't a big fan of Hector Hammond being Parallax-lite, that was a bit off, but overall some great action and great visuals.
It's not the most amazing movie in the world, but it really doesn't deserve all the crap it's getting in the reviews. I think its weaknesses are getting magnified by superhero-fatigue and 3D-fatigue.
As for the "real" Green Lantern, please don't even start with any of that "why'd they change him to a white guy?" nonsense. First of all, the Green Lanterns are a group; there are 7200 of them, so you could pick anyone and call him or her the "real" Green Lantern. More to the point, Hal Jordan was the first Silver Age style Green Lantern, and he was the Green Lantern of sector 2814 for years before John Stewart appeared in the comics, and he has the simplest and most memorable origin story of all of Earth's Lanterns. John's, Guy's, and Kyle's all come with baggage related to Hal.
Don't presume to know what you're talking about just because you've watched Justice League. It's a good show, but it's not definitive by any means.