Big 4 or 5 of Progression Fantasy

What would y'all say are the the Big 4 or 5 of this genre? When talking about the big 3, the most common two I have seen listed are Cradle and Mother of Learning, but the third is often left to interpretation. With that mind, let's make it a little easier and go with the Big 4 route, alla Metallica, Megadeth, Anthrax, and Slayer. If you're feeling cheeky, add in a fifth one to make the list odd. Thoughts?