Mainstream comics have always been a bit of a mongrel medium, poaching from every other genre (superhero comics are particularly eclectic, mixing crime drama, science fiction and fantasy, plus whatever else you might want to throw in the pot), and exploiting the fads of the moment as best they can. That's not to say comics can't be original and create their own trends, but like movies and television, they do tap into the zeitgeist and whether you want to call it a reflection of the day's concerns or cynical Roger Corman-like plagiarism, popular trends do have an effect on comics, especially work-for-hire comics.
Looking back, some trends are pretty easy to spot. The popularity of westerns in the 50s led to superhero comics getting repurposed for cowboys and gunslingers. The 60 brought back the superhero, replacing WWII with the Cold War. The 70s were all about horror, yes, but also touched on the blaxploitation and kung fu crazes. The 80s' hottest titles, Uncanny X-Men and New Teen Titans, parallel a rise in popularity for television soap operas and perhaps even an uptick in teenage angst as the decade grows more and more repressive.
It was a recipe for disaster, creatively if not necessarily financially. The bubble burst, the fad ended, and what we were left with (except for the previously mentioned exception) were ugly, risible comics we still mock and hold up as examples of bad art today. But what ABOUT today? What's popular? Not comics, certainly, with numbers as low as they've ever been and the Big 2 churning out more press releases - desperately trying to attract media attention - than JNT did during 80s Doctor Who. No, what's popular today is live-action superheroes.
Like all fads, superhero films will peter out and be replaced by the next big thing. Comics will once again draw their influences from something other than themselves. They must. That borrowing from other media and genres has always been part of their DNA, and it's what's made comics history so interesting and adaptable. That's the good news (unless you really really like superhero movies). Another piece of good news is that the best writers and artists in the industry are fighting off the staleness of the current trend, either in work-for-hire comics or, mostly, by going to the independents and crafting their own diverse narratives. Maybe the next big thing will be found there, or rather, be reflected there.
All I know is, I'm quite eager to get out of the feedback loop mainstream comics are currently trapped in.