I think it's wrong to view that behavior from dogs as motivated by love. They are programmed to be a part of a pack structure, and alpha males don't achieve their position with affection. Of course, dogs can feel affection for an owner, but their loyalty to an owner isn't necessarily based in affection. We see unconditional love, but it is an instinctive behavior. IMO if you view the behavior of dogs in this way, their behavior starts to make more sense, and is more predictable. People often talk about dogs being nice or mean, but often their behavior in a certain circumstance can be predicted by their environment. For example, a dog on a tether feels extremely vulnerable, and will act very differently based on whether or not its alpha is present. A mistake I often see people make is trying to pet a dog by extending their hand over the dog's head. This is usually ok if their alpha is present and the person has interacted with the alpha in front of the dog, but if the person has just walked up or if the alpha isn't present, the hand over the head is seen as a challenge for dominance, and the dog is more likely to bite.
I bugs me when animal behavior is dismissed as "just X". For example, cats rubbing being just marking behavior. I mean, I get that there's marking behavior but that's not just marking territory. Social behavior is complex and it having other components doesn't necessarily make it less meaningful. The pack behaviours in dogs are undeniable but that doesn't mean they have not changed and couldn't have acquired new meanings over thousands of years of domestication.
I must be so beta, I cant fathom the perspective of being the alpha of a nice dog. Plus, a cat will walk just trough that: http://i.imgur.com/9n3q5pV.gifv .. Why? Because being blocked just by the representation of a border is a trait of fully domesticated animals like dogs, sheep, cows.. Cats are still partially savage. There is an article about that somewhere on this site .. I guess.
The same is true of cats. I say they love me because I anthropomorphize them that way, but what that really means is I fit into their social structure in a positive way.I think it's wrong to view that behavior from dogs as motivated by love.