A romantic comedy starring Jennifer Lopez and directly aimed at women and an A-Team-like action flick aimed at comic-book fanboys make their debut at the box office this weekend and the winner is expected to be ... the four-week old How to Train Your Dragon. Both Lopez's The Back-Up Plan and The Losers are receiving widely mixed reviews -- mostly negative -- and each is expected to wind up with around $10-15 million. But Dragon , which has premium 3D pricing going for it -- as well as virtually all the commercial IMAX screens -- has been showing sturdy legs. It's also the only family flick in town. An apparent question mark in the minds of most box-office forecasters is the second-week potential of the R-rated Kick-Ass , which brought in far less than what analysts had forecast in its debut but nevertheless sold more tickets than any other movie last weekend.