I lived in Land Park for the last year went to the zoo a few times I wouldnt call it the best ever by any streach. I think the best ever is in San Diego wild animal park. But for a smaller city like Sacramento their zoo is pretty good and they have a lot of empty space to the right when you walk in that they can turn into something more. Overall well priced for what they have.
For those of you new to the area make sure you check out the Folsom Zoo as well. It's much (much!) smaller, but features mostly native american animals. I could spend hours just sitting and watching the bears or mountain lions.
we took our son there in the summer and he loved it. though he wasnt too interested in the animals at first. he wanted to ride the train and threw a fit every time it left without him on it, but once we were on it we had fun. the food was a bit overpriced though.