It's...okay. Uneven, a bit, but that's forgivable considering the target audience on average hasn't got the attention span to sit through an episode of Spongebob Squarepants. But the beginning part in Manhattan captures some of the 1950's love of the City of New York...and the second part, shockingly, is biologically accurate.
The second part involves the urban metrosexual lion, zebra, hippo and giraffe transplanted from Central Park to the wilds of Madagascar. On the island, they come across a huge settlement of lemurs. The lemurs live in fear of something they call "foosahs," which, in the movie, look like a cross between cougars and hyenas.
Well, surprise! The Fossa is a real Madagascan predator, related to civet cats, genets, mongooses and meerkats, evolved primarily to hunt and eat lemurs. They aren't well known, and they're rather endangered; I was impressed to find them mentioned at all, let alone featured as the villians.
Props to Dreamworks. They included real Madagascar wildlife.
As I say, the writing's uneven. There are some witty references to popular films, including American Beauty, and some wonderful depictions of Manhattan landmarks. Some nice touches include the lion's mane becoming increasingly curly the longer he's away from New York, too. It's...cute. No Shrek, but it's fathoms above A Shark Tale.