Man, I had a neighbor that had (from what I could tell) a full on, ancient breed gigantic mastiff. His head was uncomfortably close to the size of my torso. Nieghbor was BAD OWNER -- he never let his dogs inside, and basically just fed them and kept them as guards. I made slow peace with Zeus (his name). Across, the fence, of course.
Give me a year with Zeus, and I'd have him slobbering all over the house, friendly as a pup. I'd first of all train him to not jump up on people. Beast must have been close to 200 if not over.
I'd turn Zeus into a sweetheart. Unless you made a dicey move at me.
It's all about owners. Good owner + time = good dog. Unless there is just something wrong with the dog -- not every dog is wired right, and you gotta let those go. It's best for all involved.