Publishing is an interesting game. Like all business owners, some publishers are wary of risk. They want books that adhere to tried and true formulas of plot or purpose. Fiction in certain genres--think romance--even have formulas to follow. Agents who specialize in these books know the formulas and automatically reject manuscripts that don't follow them. So uniqueness isn't necessarily a winning card in your submission game.
Yet it is. More often, I've heard from agents about the boredom they feel with stories that repeat the same themes, the same trends. They look for something that will "make them miss their subway stop"--a cliche I'm sure you've heard or read about on agency sites.