Woah...woah...what?! The main reason why WoW's one of my favourite games is exactly how much it immerses me. The sound, especially the absolutely amazing music, plays a humongous part in that. But there's also the warm, versatile art style, the perfect environmental sounds and those little touches that make a zone really come alive; grizzly bears fishing in Grizzly Hills, the sand blowing over the dunes in Uldum, vines even creeping over the little flowers in Duskwood, NPC's going about their daily routines. I would never ever have played it so long if not for my longing to discover yet another jewel, hence why I usually stop playing when I run out of content.
But the music...oh good gods the music, that's really the crown on their work. I never ever understood why people just turned that off altogether.