Well, there are definitely some humans lacking any intelligence...
But seriously, of course there is a blurry line, but as far as I am concerned human intelligence is the definition of true intelligence. Of course some are smarter than others and no doubt there could exist something even far more capable than the best human, but being about as capable as a human is still the benchmark for real intelligence (to me).
If I was to get philosophical I might list something like being self aware as a defining trait, but that is also a kind of arbitrary goal post.