If you read the title, and tried to take a stab at it, I bet your knee-jerk reaction was to say Iron Man 3, wasn't it?
But no. We're talking about an original film, not one that was built around an already preexisting idea or story. That means no prequel, no sequel, no franchise, no remake, no reboot, and no adaptation.
In that case, then Pacific Rim is the big winner by a landslide. While 's robot-alien smash-up didn't fare incredibly well domestically, it did quite well for itself overseas, to the tune of hauling in $407 million worldwide, making it the tenth-biggest earner of the year. To give you an idea of how heavily Hollywood relies on preexisting ideas, Pacific Rim was only one of two original films in the top ten this year, with The Croods being the other.
China was by far the biggest market, accounting for a quarter of the films total revenue, which almost guarantees we'll be seeing a sequel, seeing as how Hollywood is desperate to jump into bed with both Chinese financiers and audience.