Since everybody else is comparing Beauty and the Beast to The Little Mermaid, lets be a little different and compare it to another Disney animated feature: 1981's The Fox and the Hound.
While that film had some good animation, it was presented in a rough, haphazard form; Beauty has equally good animation and is among the most opulent Disney features of the past fifty years. Fox told its story in a bland, episodic way; Beauty makes its very old story involving from start to end. Most importantly, Fox and the Hound was a film made by artists who had lost touch with their audience but Beauty and the Beast promises to be a huge mainstream hit.
Obviously, things have changed a lot at the Disney studio over the past decade, and most of the change has been for the good. While Gary Trousdale and Kirk Wise's film may not be the instant classic that it's already been labeled, it's an extremely winning musical romance thats inventive from start to end.
The movie isn't a carbon copy of The Little Mermaid, but there are decided similarities in approach. Both movies go for the Disney roots by being lushly adapted fairy tales, yet are distinctly products of their own era.