SO subjective, hahaha, but its fun to see everyone's taste preference.
My own personal order of preference would be: Bison, Stone sheep, Elk, Moose, Mountain goat, Bighorn, Blacktail, Mule (same species, but I taste a big difference between coastal blacktail and mulies east of the mountains), whitetail, and then Caribou way down at the bottom (too much lichen, I suspect).
Obviously, the animal and circumstances make a massive difference. I have heard a young female caribou is really good, but I've never had it and what I did have was tasteless and very gamey. I wasn't a fan of Elk, at all, until a friend who knew what they were doing cooked up a tenderloin from a female. Then I became a big fan. Smoked Muskox is really tasty too, eaten with dried blueberries. I've had Red deer before and it was delicious.