If you were a veterinarian would you be a good Human Doctor?

Not necessarily. There are some people with both degrees (DVM/VMD and MD/DO), but they are quite rare and tend to be in research rather than clinical practice.

Veterinary medicine is a broad, comparative anatomy-based science that relies primarily upon the deductive reasoning skills of the veterinarian. In some disease conditions, veterinarians use "response to treatment" as proof of diagnosis - if this works, that was what it was and now we are all better. Veterinarians can and do euthanize patients who cannot be treated or who cannot afford to be treated.

In contrast, human medicine is a narrow, species-specific science that relies equally upon the medical knowledge of the physician and a wide array of diagnostic machinery and tests. Physicians are generally not allowed to use "response to treatment" as a diagnostic test - this is called malpractice. Physicians can never kill a patient because the person was unable to pay for medical care (this is grossly unethical), and in most places also cannot be involved in physician-assisted suicide.

Many veterinarians choose animal medicine over human medicine for a variety of reasons; as they progress in their careers, their reasons tend to solidify rather than break down.