Animal Forest is the Nintendo 64 version of
Animal Crossing. It was made before "Animal Crossing" obviously and was only released in Japan. It's a de-graded version of Animal Crossing.
Animal Forest+ is the Japanese version of Animal Crossing for
Gamecube, but it has more features than Animal Crossing. It isn't going to be released in the U.S. because half the features were already in
the U.S.'s Animal Forest upgrade for Gamecube, "Animal Crossing."