The bullseye or bull's eye has, since 1833, been the name for the center of a target and, by extension, since 1857, has been given to any throw, toss, or shot that hits the center. In further development, success in an endeavor in which there is such inherent difficulty that most people are far more likely to choose, do, or identify something that is either unfortunately only close to or dismissively far from the ideal or necessary thing to choose can be called "hitting the bull's eye."

Source: Wikipedia