Do you really believe your dog loves you unconditionally? I know many people say that jumping around when you get home is a sign of love, wagging their tail, barking for you, excited to see you is all love... but I have to heartedly disagree. I tend to side with Cesar Milan on the mindset of dogs.

(Not an exact quote, rather an idea)
Dogs don't think about how you feel, or why your feelings are hurt when they do a certain action, they know that they can act aggressive/mopey, and get the desired result from the human. They are conditioning you.

I still have to say that animals rely specifically on learning behaviors and instincts. I don't believe they love, but their degree of security to the point of pleasure and affection is enough to make people believe that they are "loving" us as we love them.