Yep, I liked the movie as well and I am a pretty decent, knowledgeable Green Lantern fan. 

It was absolutely no better/worse than the Marvel movies that came out at the same time.  There were other factors at play that worked against the movie.

-  The release was timed poorly.  It was a Fathers Day release (... unfortunate development if you are attached to fathers in this movie ...) which closely followed a Marvel release in May, so there was an element of audience superhero movie saturation at play

-  It was an (relatively) expensive movie die to the GL CGI SFX, I guess.  Therefore, it had a higher first weekend breakeven box office threshold.  It actually came CLOSE to meeting the assigned box office revenue projection, but fell short -- therefore it was labelled 'a flop'.  In retrospect, its take was comparable to other non-sequel superhero movies.

-  Being labelled 'a flop' or more fairly, 'a disappointment' left the movie open to all kinds of negative narratives -- particularly Hal Jordan's characterization, Geoff Johns influence/involvement in the film, Ryan Reynold's performance. 

I don't know ... I believe that GREEN LANTERN is a good, enjoyable superhero movie.