We love singapore. If you are foodies, then no trip will be long enough! I would say for a first time visit 4 nights would be a good time. Enough to find your feet, explore and get some good eating in!
We have been twice this year, each time for 5 nights, and still felt we wanted to say longer. There are a few people who say Singapore is boring and 2 nights are enough, but they cant have even scratched the surface!
I can highly recommend the Conrad Centenial hotel. If you can run to it, get an executive room with club floor access. You will save yourself a small fortune in drinks bills as you can get alcholoic drinks there all day till 11pm- booze is pricey in Singapore! Afternoon tea and evening cocktail nibbles are also provided, so you can cut back on spend outside the hotel.
If you want more info, post fao me, and i can tell you some things to do and good places for eats!