I’m familiar enough with the comics to know that it’s really the ring that matters (though I guess he could wallop bad guys upside the head with the lantern if he had to), and that green fists are going to be involved. So, I can’t speak for fans of the printed version(s?), but I liked Green Lantern.
I think a lot of people were expecting Ryan Reynolds to be a poor choice, because they associate him with some of his comedic work (e.g.: Van Wilder). I had higher expectations because I really liked Definitely, Maybe, and not for the comedic moments but because I thought it was well-acted.
So, going in, I had medium-expectations, and was pleased when they were exceeded. It’s not Iron Man and won’t revolutionize anyone’s career nor be considered the kind of revolution in movie-making that Spiderman was. But it’s plenty entertaining, it has a good comic-book feel to it, and I love the bit where Blake Lively's character meets him and gets a chance to actually say “hello” and thank him for her rescue.
I don’t think it’ll be a spoiler when I say that he saves Earth. I liked how he did it. Totally wrong physics, but it is a comic book movie!
So, 7 on a 1-10. Entertaining, fun, don’t pay for IMAX but it is worth the big-screen in a normal theatre if you don’t have something with similar perspective at home.