Talking animals are fun.
In the same way that talking babies were fun in the countless "Look Who's Talking" films, or Mel Gibson's ability to read women's thoughts was fun in "What Women Want." The list of novelties goes on indefinitely - would Paul Hogan even have a career if not for the "Oh look, an Australian! Say `mate,' say `mate!'" reaction evoked by the "Crocodile Dundee" films?
All these films are one-trick ponies, and their success relies on the mass appeal of those tricks.
So whether you enjoy "Dr. Dolittle 2" or not ultimately depends on whether you buy the film's gimmick - you either love the talking animals or you don't. If talking animals aren't your cup of tea, then this will be the one of the worst film experiences of your life.
If you do, however, you'll be rewarded. Not as handsomely rewarded as you probably were in Eddie Murphy's first "Dr. Dolittle" film, but rewarded nevertheless.
The film picks up after Dr. Dolittle (Murphy) became a doctor to animals of both the two-legged and the four-legged variety. In the time since, Dolittle's ability to talk to animals has made him both a very successful doctor and a celebrity, garnering the attention of a woodland-creature mafia who want the good doctor to save their forest from the evil white corporate leaders you see in any pseudo-environmentally conscious film.
In order to save the forest from corporate ransacking, Dolittle must make sure two bears of the same endangered species mate. The catch is that Ava (voiced by Lisa Kudrow) is at home in nature; Archie (voiced by Steve Zahn) is a circus bear.