Yes, you and @natureofbeing have hit upon the same thing, it is the passion and emotion that makes a great work what it is. However as I mentioned to @natureofbeing, perhaps once these machines are sentient, we will start to see another type of emotion in them, ones that we don't recognise yet find fascinating.
Check out the AI art link I put under further reading, it's just a few pictures, but it's very interesting, mainly because they are not recreating what they've seen, neither in detail or style.