This is a question that has bothered me since young. I never found a satisfactory answer to it. Yes, I hate harming animals such as cats and dogs, and do consider them almost, but not quite, equivalent to a human's. But I am not a vegetarian. I eat beef, chicken, red meat, etc., and have never held the seemingly "less intelligent" or "less human-like" animals such as cows and goats in the same regard as cats and dogs. Why are some animals of higher stature in our eyes and others not? Simply because they've adapted to our notion of "intelligence" or "cuteness"? The perceived danger the animal poses probably plays a huge factor as well. What about little insects such as ants, irritating pests such as mosquitoes or dangerous animals such as venomous snakes? Personally, I definitely do not hold such animals in the same class as traditional household pets.
I know other people I've asked simply say you'd be crazy to treat an animal equivalent to that of a human's. If an animal (say, your pet dog) and a human were about to run over by a train, and you could only save one, which do you choose? If you truly valued the life of an animal to be equivalent to a human's, this would prove a true dilemma. For me, I would choose the human, but no, I do not think it is "crazy" if you chose otherwise, especially if the human is a complete stranger (or worse, some criminal) and the dog had been your lifelong companion.
Thanks for the question. I would love to hear others' take on this.