There are cats out there that show love for their humans, but not all of them do. I've encountered many cats that just ignored, ran away from, or showed aggression toward humans. However, I've never met a dog that did not seek interaction with humans.
Here's another little tidbit: When a person is interacting and bonding with a dog, their brain releases the same hormones (hormones? maybe neurotransmitters? I'm not sure, something in the brain) as a mother's brain releases when she is bonding with her newborn child.
Also, there's a reason Fable gives us a dog instead of a cat.