I'm not making that up, Neil Gaimen even reflected it in his graphic novel Whatever Happened To The Dark Knight? Which was kind of a response or reflection of Alan Moore's Whatever Happened To The Man of Tommorrow? A more sensitive treatment of Superman but each book dealing with a Last Issue or The End of The Series Issue.
Some commentators see this as the comics or their readership or writers "growing up" or "progress" but I reject that completely, I dont see how trashing something in the course of a supposed "critical evaluation" is producing anything of any worth, another example is Judge Dredd, he started out as an authoritarian but sympathetic character, perhaps like Dirty Harry or John Cobra or movie cops of the eighties, but with publication of story lines like Amerika became just a fascist who it was only possible to incidentially or involuntarily sympathise when they faced off against greater, meaner, eviler odds, like Death, demons or mutants.
The Punisher is one of my personal favourite characters and he evolved rapidly from a character who it was possible to sympathise with to one it was only really possible to appreciate as a real anti-hero (although I think something similar happened with the Death Wish franchise) and much of the time not even as that. He's often contrasted with Dare Devil, there was more than one storyline comparing the characters, as the evil conterposed to the good. His first incarnation was a veteran war hero who was avenging his family's murder. Writers and artists even went back to his time in 'Nam and depicted him as psychopathic back then and psychopathic all along rather than heroic.
V for Vendetta and The Watchmen where in their own ways both major critical responses to superheroes as a genre altogether, even more apparent in the comics than the film adaptations but still pretty obvious even then.
There's without question a trend there, I very much doubt its a matter of any swing back and forth in taste, its not something so simple as a new "dark" side of the character being shown in response to the "foppy, boy scout" persona, Tim Burton's Batman was dark, the original Batman was dark, in one of his first scripts he abandons a mad scientist to burn in a house fire and he even weilded guns and shot criminals.