I'm not sure I would call it an "Amusement Park". First of all, it doesn't have any rides. It's more of an interactive aquarium than anything else.
I suppose it's a gray area given how many "category-blurring" theme parks exist now. Regardless, Discovery Cove is amazing and certainly worth a visit for anyone who enjoys dolphins, snorkeling, and an open bar. :-)
Reason #2 to question these results: They put Hollywood Studios as #4 (behind Islands of Adventure and Magic Kingdom). Assuming this is a global award, NO ONE who knows anything about theme parks would put Hollywood Studios in the top 10, perhaps top 20!
I've never even heard of Discovery Cove until this post