Now, I haven't been to any zoo BUT Milwaukee County Zoo, but I'd have to say, it's great. The exhibits are always clean, the animals are always well taken care of, and the special attractions are worth going to the zoo for. Fun for all ages, you could spend an entire day there without being bored.
If you do go, be sure to check out the train! It's my daughter's first stop when we go, and I have to say that at 24 years of age, it is my favorite part, too. It goes all the way around the zoo and you see everything!
Be sure to check out Skate through the zoo and the night events, they are all fun.
Get the family together and get out to the zoo!