His range is trully outstanding in relation to the rest of popular music. But, as has been said, its not just the notes its the way he puts them together. There will be many who couldn't get as low or as high as Elvis and much of the time that will be physiological but for me one moment, out of many, stands out where it is more than physical range but pure musical talent and ability.
In recordings of Just Pretend, and as seen on TTWII, when he does the "whoa-hoa-hoa-a-whoa-hoa" (y'all know what moment I mean

) that is mighty, one of my all time favourite Elvis moments.
I've been a singer for about 20 plus years now, choral singing, leading singing, entertaining and was cantor in Ireland's national seminary, I'm a fairly good singer but for years now there is just no way I can emulate that. The rhythm, the inflection, etc. And Elvis knows it too, look at his smile.
Another moment where he's not just the singer, he becomes the song itself.