Below excerpt taken from http://www.petcentric.com/Read/Articles/Do-Dogs-Feel-Love.aspx?articleid=792a5e32-3030-4453-ae9f-5f48b093f98e :-
Dogs Give Unconditional Love
Dogs taken from abusive situations hold no grudges toward the human race. A half an ounce of kindness from a new person results in an abundance of affection from the formerly mistreated dog. Humans rarely have the capacity to so completely forgive and love under those circumstances.
Probably the biggest reason the dog has become man’s best friend is because we know that when it comes to love, a dog can always outdo us. The highest form of love, agape love, which is completely unconditional, is something that people often have to work at or grow into. Agape love seems to come naturally between parent and child, but it’s more difficult between husband and wife, and harder still between friends. To love someone regardless of what wrongs they have done you is very difficult for humans.
A dog, however, is born with an endless capacity for unconditional love, and doesn’t even have to work at it. You can be a complete grouch, ignore your dog, and refuse him your love. When you decide you’re ready to be sociable again, your dog doesn’t pay you back by ignoring you too. He’s just happy you’re there. More amazing still, is that the love that dogs and owners feel for each other lasts a lifetime. This is the ideal love humans strive for, but often fail at.
As Jeffrey Moussaieff Masson so beautifully writes in Dogs Never Lie About Love, “Learning to know somebody intimately is often the beginnings of dislike, sometimes even of contempt. Among humans, love often does not survive a growing acquaintance, but in a dog, love seems to grow with acquaintance, to get stronger, deeper. Even when fully acquainted with all our weaknesses, our treachery, our unkindness, the dog seems to love strongly – and this dog love is returned by most humans. We, too, seem to love our dogs the more we get to know them. The bond grows between us and our dogs.”
This is why we need dogs. They do something for us that rarely a human companion can do. No matter how much you mess up your life, or how much wrong you do, no matter how many mistakes you make or how often you make them, regardless of your looks, income or social standing, your dog never judges you. He always thinks you are wonderful and loves you with all his heart.