I think it is okay to say, "Dogs are the animals I like best."
Are the following sentences acceptable?
1. The animal that/which I like best is the dog.
2. The animal that/which I like best is a dog.
3. The animal that/which I like best is dogs.
I learned that "a dog" can be used as a collective term only if it is used as a grammatical subject (i.e., "A dog is a faithful animal.")
Therefore, "I like a dog" does not mean "I like dogs."
"I like a dog" may be used if I go to a pet shop to buy a dog.
"The dog" can be used as a collective term, but I don't think we can say, "I like the dog."
However, "Today, we learned about the cat at school. Lions, tigers, and cheetah as well as cute cats you find in town are members of the cat family." seems okay to me.