Apart from the view of the city from the Marina Bays Sands Sky Park and the dizzying height of 1 Altitude Bar at One Raffles Place, there is one unexploited (well, unexploited by tourists) place in Singapore with a breathtaking view of the city's skyline: the Marina Barrage.
It is actually a dam with a park on it's rooftop. On any given day, it is a regular park full of families and youths having picnic and flying their kites. But I would think it's best to go there at night where you can see the city lights from afar.
Photo from http://news.gov.sg
