First, I was impressed with Baltimore’s Aquarium, then more so by Seattle’s; and then I was sure the Monterey Bay Aquarium was the pinnacle. But recently I visited the Aquarium of the Pacific in Long Beach, and it became my new favorite. I also heard there may be a better aquarium in Europe.
For the price (free) however, I also thought the Aquarium at Santa Monica Pier was also nice. It’s more geared toward school-kids and does a good job tackling conservation and water quality.