They have meaningful Musica that people can relate to and that help people, not just stupid Amore songs no one cares about. Also the lead singer is gorgeous.
Because of the variety they have, the songwriting, the vocals, and I just like the songs in general - from the catchy ones to the metallic ones to the beautiful orchestral masterpieces. They appeal to my dark romantic side, my aggressive side, my upbeat side, my calm side, and even my interest in mythology. ;)