What are the other Animal Guides?
It's impossible to say whether the other avatars had Animal Guides. The only ones we see are Korra's, Aang's, and Roku's. Kyoshi, Kuruk, Yangchen, and Wan were never seen with one. Of those, Wan was the only one we really got a lot of backstory for and he was never seen with an animal guide, though it seemed Ravaa may have been the equivalent for him.

While the earth kingdom avatars are never seen with an animal, if the other three avatar animal guides we've seen are indicative of their respective elements' animal guides then it would be:


Dragons for Fire Avatars
Air Bison for Air Avatars
Polar Bear Dogs for Water Avatars.


There isn't much information that I could find on this subject, so this is the best answer I was able to come up with