I didn't go to any theme parks in Singapore.
Awesome places to check out though were Sentosa Island, for which you would need at least a full day.
Also the Singapore Zoo and Night Safari were really interesting.
So, not quite theme parks, but they are all parks of some description. about 8 years ago
Depends on when you are traveling to Singapore. Next year (or 2011) the Universal Studio's Theme park will be opening down at Sentosa Island, and later next year the Integrated Resort (IR) will be opening in Marina Bay - but this is more for gamblers. Otherwise there's not much of a choice for theme parks here :( maybe try Disney World in Hong Kong. over 7 years ago