There are a few recent pop songs which I've heard for the first time on the X-Factor, and subsequently got really hooked on. Best examples from this series would be Katy Perry's 'ET' (performed on the show by Amelia Lily and Littlemix) and 'Jar of Hearts' by Christina Perri (Craig Colton). I now love these songs. Sometimes the live act's take is more than a match for the original, or provides enough of a twist on it to get you interested.
As someone who doesn't really follow the charts closely (any more), I like the idea that there is this well of quality pop music to be tapped into, which The X-Factor is a celebration of, in a way.