I have never been to any oceanarium so I had no point of comparison. But based on the photos, I can say that it isn't too behind with its Hong Kong and Singapore counterparts.
Here are some information about Manila Ocean Park, from http://www.manilaoceanpark.com
Admission - General Public
Adults : Php 400.00
Kids (4.5 ft and below) : Php 350.00
But just fresh from Holiday season, the Manila Ocean Park has a promo where just with an additional 100 pesos, one can get a tour of the Oceanarium, plus variations of having a boat ride, fish spa and encounter with jelly fish! We chose to have the Manila Ocean Park fish spa and Manila Ocean Park Glass-Bottom boat ride.