The PMP is extremely popular. Currently there are over half a million PMP certified project managers all over the world, with a large concentration of these PMPs in the United States.
It is true that most companies nowadays demand that the candidate for a project management position to be a PMP (especially if the role is non-senior) - but there are some companies who don't. However, all companies consider the PMP to be a plus on the CV, so the PMP is actually an excellent certificate to have.
PRINCE2 is far, far behind the PMP when it comes to popularity and adoption. The PMP is by far the best and the most respected project management certification out there. (Note: There are some companies, especially in the US, who don't acknowledge PRINCE2 as a PM certification)