For a special romantic dinner my wife and I choose Rockhouse, and sometimes Xtabi. Both are a short ride away up on the cliffs with great sunset views. I suggest making a reservation for before sunset and asking for a table with a view when you make the reservation. Both restaurants will pick you up from your resort for free, but you need to pay your way back. (Negotiate that price before getting in the cab).
Alfred's and Cosmo's are also very good, and are more casual. They are also closer to both Couples resorts than the places up on the cliffs. For a special dinner though... Rockhouse would be my choice.