There is no 'higher' or 'lower'. It's only from our point of view that such hierarchies are 'seen'. I'm sure the angels and 'higher' beings are prone to such thinking as well, and they're just as much guessing about the mystery that is existence. They may all have more *knowledge* about the universe, and be incarnated in a nice place for millions of years because of good actions but it doesn't mean they're all-knowing..
OTOH, a lot of humans do seem to have the right amount of suffering overall yet not too much enjoyment either..
But every life form is unique. I do agree human life is very precious spiritually because of the potential, though it doesn't make us higher or better, just lucky. In any case, our 'privileged' position and unimaginable, large impact indicates we have a responsibility.