The other night, in discussion with friends of mine, it came up that most every generation of creators seems to be influenced by whatever happens to be in popular culture at the time. Previous generations were influenced by Star Trek or Star Wars; the last generation or so was influenced by the first wave of anime crashing on American shores; the current generation is surrounded by Harry Potter and now love-triangle YA dystopias.
I would need to do more detective work to confirm this, but it seems about right. What I find most important, though, is how any given generation of creators is able to take what they're surrounded by and transcend it. It's easy to create something in the mold of what you and your audience were reared on, but most of the time the end result is self-limiting and forgettable. It's far harder to look around, ask "What is everyone not doing and why?", and come up with a memorable response.
Copying what's around you and presenting that as if it's original is no great sin, but no great achievement either. If there's a reason The Mortal Instruments seems vaguely reminiscent of Harry Potter with the serial numbers filed off, that's because it was exactly that, and that also explains why it didn't have one fraction of the impact of its predecessor. People can tell on some level when they're experiencing something following the familiar close enough that it treads on its heels, even if they aren't always capable of articulating that fact. But they know it, and they respond by having their interest in the thing in question peak quickly.
A fellow author once put together some advice for prospective beginners. One of the bullet points was to watch or read other things in the same genre as your prospective work. I thought this was well-meant, but ultimately redundant. The odds of people by default reading/watching in the genre of their chosen project is much greater than the odds that they will try to draw on things from outside of that bucket. It makes more sense to encourage them to move away from what they (and their audience) know and are comfortable with.
The reason for this is something anyone who's read me for more than two seconds ought to know by now. The truly new thing may be a pain in the ass to deal with the first time, and may be harder to get to at all, but is far more worth it in the long run. And sometimes one of the only ways to get there is to take that many more steps away from what you and everyone else knows, whatever the cost in discomfort.