For a movie in which the hero has a color in his name, Green Lantern has some of the drabbest and least colorful visuals imaginable. (I am one of the few defenders of Jonah Hex, but it too has "dark" visuals for a movie with a surprising number of quips-- it probably has more jokes in it than Green Lantern.)

I think the "gritty" thing people jump to is just in response to the assumption that Nolan and Snyder will have their hands in the cookie jar for almost every coming release. I do agree it's unfair to assume something like Shazam would be dark and murderous.