I didn't say anything about the plot. I suppose it worked; the plots to most movies do. Plot is also the least interesting aspect of film for most moviegoers and in most cases is the element that has the least bearing on a film's success.
I know you enjoyed this movie and would like to believe that it had some sort of depth and humanity that audiences and critics have simply been unable to appreciate, but that has everything to do with your bias going in, and little to do with the merits of the film.
Iron Man was a huge success because people connected with the main character and, to a lesser extent, the supporting characters. That is the measure of a film's "humanity": does it make you care and relate to these fictional constructs that are all, at the end of the day, basically just variations on the same themes and tropes?
Thor was also able to do that as well, to a lesser extent, because the director and cast elevated a competent but unremarkable script evoking a mythos that is wacky and unintuitive, even by comic book standards. There is nothing in GL that comes even close to the depth of Loki's conflicting emotions when he learns of his true heritage, or Thor's heartbreak when he finally understands the full measure of his situation ("Can I come home?").
GL has its moments, but at the end of the day it is not going to be a critical or financial success because it didn't give audiences enough of a reason to care about the main character or his entourage. A difficult production and technical shortcomings no doubt contributed to that.
Comic book movies are a bit of an odd beast, in that they cannot get away with being dumb action flicks like Fast 5. These types of stories ask more from the audience in terms of suspension of disbelief and emotional engagement. The successful ones infuse the material with an emotional depth that transcends the formulaic aspects of the genre; the unsuccessful ones do not, generally speaking.