The Cleveland Zoo has some great exhibits. We enjoyed the animals and most of the staff we encountered were friendly. As others note, it's also very affordable - much more "bang for your buck" than the aquarium.
The reason I deducted 2 starts is because it's not very user-friendly for special needs kids. For example, the train in the "Australian Adventure" part of the Park has a recording that's extremely and unnecessarily loud. My daughter has a sensory disorder and the noise terrified her. There's also no warning that these recordings are used, which makes it impossible for parents with children who have sensory disorders or autism-spectrum disorders to know that these exhibits are unsuitable for their children. To me, the recording is an access issue, and a place that caters to little kids ought to have been more aware/sensitive to something like this.