Horton Hears a Who!
The answer is yes... for the most part.
The character and set designs are pure Dr. Seuss, as is the narration in rhyme. Nods to other Dr. Seuss works abound (green eggs are on the breakfast table, Horton is reprising his line from Horton Hatches the Egg and more) but don't interrupt the flow of the story. Who-ville has the surreal architecture and technology that defies gravity and common sense yet works in a Rube Goldberg kind of way. Some material is added here and there, but it doesn't feel like padding; not only does it nicely round out the story, it adds to it without losing the spirit of the original.
Which brings us to the theme of the movie. Rather than being about the value of everyone's contribution to society, no matter how small it is, this Horton movie is more about acceptance. It's about accepting other people who are different and it's about accepting the fact that those you love may not always do what you would like them to do. The mayor (now overshadowed by the town council) must get the Whos to accept him and what he has to say, and he has to accept that Jo-Jo (now his son) does not want to become the next mayor of Who-ville. The jungle animals have to accept that even if they can't see or hear or feel a thing, it still exists.
Horton, being Horton, is the only character who doesn't need to learn this lesson. His mind, with a childlike curiosity about everything around him, is what makes him so charming. We get to visit that mind a few times during the movie via a few 2D animated sequences representing his thoughts and imaginings. Overall they are rather disappointing, especially when you compare them to the original cel animations featuring Horton or the wonderful 3D work done by Blue Sky. It also would seem to me that the mind of such an imaginative and childlike character would be more colourful and surreal—in short, more like a Dr. Seuss book.
That aside, the film still captures the imagination and sense of fun the way Dr. Seuss did so well. Horton Hears a Who! is definitely worth the price of admission for both parents and kids.