A top-10 list indicates 6 primates, cat, dog, and cow. While there has been a lot of testing done on primates and dogs, they are much more sympathetic for animal-rights groups, and the general public, when protesting vivisection, breeding, and confinement.

Anatomically and behaviorally, primates would still be the top choices there. And many, many disciplines experiment on animals, where results don't come at the genetic level.

Good, the genetics match closely. But mice (or rats: see the idiom "lab rat") are also considered vermin, prolific breeders, fit in your hand, short life-cycle, and easily obtained. So they join fruit flies in the lab experiments.

Interestingly, pigs are used in many types of medicine while not enjoying that genetic similarity. In the 1950s and 60s, your insulin and thyroid meds were often derived from pigs.