I think the best superhero movies are when the characters are flawed in some way and try to change. They really emphasized Tony Stark's callous arms dealing, just like they stressed Thor's arrogance and Spider-Man's insecurities. In the first X-Men movies, Wolverine carried the whole thing with his feral "man without a past" shtick.
You've got to grow with the characters in order to feel involved, and with less successful movies you don't. Like in Daredevil, Matt Murdock's character arc was all over the place, and in FF I didn't feel much for the characters at all because everything in that movie was pure popcorn.
I haven't seen GL, but if they didn't get the "hero's journey" thing right then I have little hope for the movie.