Luhrmann has balked at calling it that, I'm told. The concern is that "biopic" too strongly connotes cleaving to the already-known history of the person and depicting it somewhat in a "paint-by-numbers" approach. Luhrmann consciously chose not to do that.
From what little I've seen, the acting and writing look really, really good. I'll always favor a good story told well over one that gives me something I was already looking for. Also, Elvis was the King, man. For all that was wrong with him, he did show us that the actual limits of human potential are a lot higher than we suppose. Kind of like Mozart did, but this time with the blues and rock and roll.