I don't really know but my first instinct was to go with elephants, so I'll go with that. I only really love one elephant, Margie, but I think their character model is absolutely adorable and could have even better designs than they already do. I also absolutely love the sheep too though, and I actually like more sheep than elephants so idk.
I know it's kind of a lame choice, but I'd go with cats. Their model in every game so far looks really good (especially like the pointy ears). Almost all of my favourite characters excluding Alfonso and Tom Nook (yes, I like him) are cats such as Bob, Rover, Tangy, Mitzi, Punchy and Rosie. My second favourite would be wolves, again due to their pointy ears and the way their model looks like in every game.
Sheep, wolves and hamsters! At first I wasn't overly fond of the wolves because of the way their mouths move, I used to think their lower jaw was too big and it almost looked disturbing for a while. Then I got used to it, now I love the wolves in general. Then again I have a thing for wolves irl, so I had a feeling it was only a matter of time before I grew fond of them.
Sheep and hamsters are simple enough to explain why I love them. They're so spherical, it kills me.
I love cats and squirrels. Most of my residents are one or the other and my two favorite villagers of all time, Static and Tangy, happen to be those species.