Considering the fact that we interbred with H. neanderthalensis and H. denisova (and still carry the residual DNA to prove it), I think it's pretty well proven that considering only H. sapiens to be "human" is overly narrow.

Personally, I would argue that anything within the Homo genus is human by definition (that's what the word means!), and that anything non-human belongs in a genus like Australopithecus or Paranthropus instead.