Easter has been the most important Christian holiday for most of Christianity's existence and I would argue that it still is among devout Christians. Theologically it is definitely more important.

I think the traditions that Christmas has sycretized make it ideally suited to being a more popular holiday today among non-Christians and the less-devout: gift giving, interesting characters (St. Nicholas/Santa/etc.), the various Yule traditions, not to mention being a great holiday for retailers to exploit and advertise. Comparatively Easter has less going for it to entice the non-devout.