Soulfly is definitely nowhere near death metal; Sepultura's early records could be called death/thrash metal. But Soulfly? Stylistically closer to new metal.
Anyway, don't forget Death! I've only recently got into Sounds of Perserverance, and I can't wait to get more. Schuldiner was incredible; a terrible loss. I do remember Leprosy; my 14-year-old self thought it looked rather extreme. Now I'd probably think it was good thrash metal. Nobody said "death" metal back then. I first heard that in the early 90s. Does anyone know when the term "death metal" became popularised? Probably when more and more such bands were coming out of Florida: Morbid Angel, Death, Obituary, Cannibal Corpse, etc.