Which animal makes better pet? Why?

I don't have a pet, but I want to have pet in the future. I will have more free time when I will be old woman,and I may be going to lonely. I think the animal is dogs, because dogs especially have power of healing. I think dogs need masters. For example, when a master go back home, a dog approach a master. May be the dog is very happy then. I often hear this experiences. It is very enviable existence for me. I want to have a dog sometime!!