In no way am I saying every painting about Death is breathtaking, every movie about death is a classic etc. This is directed towards people who instantly hate Death Metal because they see songs about Death as stupid, grim and depressing. Just because a song has a theme that isn't about happiness, doesn't mean the song isn't enjoyable.
Death metal has some of the greatest lyricist and musical composition I've ever heard, especially bands like Death, Possessed, Atheist and Wintersun. Death metal lyrics [for the most part] are made to go to areas most other artists are afraid to touch, mostly death and dark subjects.