Of course, as we know, there are many variables - age, sex, health, circumstances of the kill, field dressing, care in the field, weather/temperature, and the quality of the butchering, etc.
However, all things being equal, my favourite (and our staple) is moose, with caribou a close second. Caribou is finer grained and therefore on average it has a tendency to be slightly more tender than moose.
But, we also like (and regularly eat): black bear, beaver, snowshoe hares, geese, ducks, grouse, ptarmigan, and other.
We live north of where whitetail deer range, but I have often traveled to hunt them, and that venison would be a close third on my preference list.