There's always another gimmick out there. Another "well let's twist this genre in this direction this time" approach to plotting. It gets formulaic pretty fast. For example:
The Journey/Quest (classic storyline):
1. TJ + lost heir + evil overlord
2. TJ + mystical talisman + elves
3. TJ + band of thieves + dragons
4. TJ + complex magic system + lost utopian land
Dystopian future (popular storyline these days):
1. DF + plague + evil regime
2. DF + mystical old technology + mind readers
3. DF + nomadic society + mutated animals
4. DF + controlled society + rebellious movement
That's the neat thing about basic story structure, getting to play with it. The thing to watch out for is making sure you're not spending all your energy on the twists and gimmicks. Give the reader some good characters to bond with.
Not just high concept characters with heroic attributes, we need personality. I don't know if it's fear of not coming across politically correct or neutral or catering to the supposed stereotypes that are popular (such as the bad-girl heroine or the sarcastic teen) but I've seen a dearth of personality both in unpublished and published stories. All the weight of promotion is thrown after plot gimmicks or twists and while we can marvel at the writer's brilliance with such, afterwards, the characters of all those books meld together in a rather bland stew. Am I the only one who gets an "I've read about you before" feeling?
I struggle to think of a single character I've read in the last five years who really stands out for having both a memorable personality and likeability. (Some characters have come close.) Villains get better personalities sometimes than the heroes. Sidekicks will even tout more characterization, which causes another issue in that they can take over the story because of it. Is it so bad to have a heroic character with a personality disorder, a speech impediment, stranger ideas of how society should work, or a practical joker? Can that tough heroine ever chill enough to be vulnerable or even better, hilarious? Can that teen on the cusp of radical discovery within your world ever do anything silly or clumsy—on purpose? Why are we so serious all the time with our protagonists?
Think about your favorite characters (not plot devices) in books and films. Why do they stand out to you? What is it you love about them? What makes their conflicts so much better because of their personality?
Of course, this brings up the issue of stereotypes. Yes, characters can be cookie-cutter. I think that comes from a lack of personality too. We can assign traits or flaws to characters, but their personality (their actual character) defines how they react, how they think, what they say, and what they decide.
So say you want to make your protagonist a fairytale princess. Okay. Automatically you know what goes into that type of character based on stereotypes. Let's say you assign her a flaw, like a limp or a lisp. That breaks the stereotypical mold a little. Now analyze her personality. Not just things you'd like her to be angsty or excited about, but really think about what makes her tick. Look at her as a person more than as a stock character princess. What does she want and why? What does she do that makes her stand out not only from other princesses but from all the other characters in the story? What is she willing to do to achieve her goals and better yet, what isn't she willing to do? If she's forced into a situation where she must do something she never wants to do, how is her personality going to react, adapt or fail?
Stock characters are easy. Characters with personality take more time and loving care to craft. I think it's a pity when I read a book or see a movie where the plot twists and gimmicks are clever, but the characters fall flat on their little stock faces. Characterization will stay with an audience longer than a plot will. Give your audience characters that stand out and even better, that they can love, and they'll come back. Not only for other books, but also to re-read the stories you've already created. A story someone will come back to over and over again usually becomes a classic and doesn't die-out in the flames of the next big thing. While consistent story output is good to develop a brand and keep that brand alive, quality of the product will do a whole lot more.
Don't be afraid to let your characters be somebody. No, not everyone may like your non-stock character but others will love them. Even the haters will find they will remember your character long after they've forgotten cardboard cut-out characters from their favorite plot-driven stories. Have fun, enjoy the writing process here. Well-built characters tend to make the writing flow better and you'll not need to sit back and wonder what they would do in any given circumstance. Don't stress over making your hero or heroine sound and behave just like the characters in (insert popular or classic story.) There may be only a handful of basic storylines but there are billions of diverse people out there.
Let your characters work hard for you after the book is closed (or turned off, as the case may be.) You want them to haunt the thoughts of your audience. Make them memorable. Give them a personality.