If I was to narrow my list down to my five favorite metal bands. Considering longevity, originality, diversity, and re-playability. It would probably be...
1. Ulver
genre's covered: Black Metal,Pagan Folk, Ambient,Electronica/Trip-hop,Prog-Rock, Chamber/Classical
2. Opeth
genre's covered: Death Metal, Folk, Prog Rock
3. Devin Townsend (I'm counting all of his many side-projects and metal band incarnations)
genre's covered: Prog Metal, Ambient, Electronica, Death metal, Speed Metal, Jazz-Metal,Punk
4. Between the Buried and Me
genre's covered: Grindcore, Speed Metal, Death Metal, Pop Metal, Emo(ish), Punk
5. Fantomas - Fantomas defys all genres
honourable mention: Meshuggah (the only reason they didn't make the list is that they aren't very diverse, but they have made some of the best metal records I have ever heard) *cough*Chaosphere*chough*