Without a doubt (IMHO), the most luxurious hotel in Singapore is the Valley Wing (hotel within a hotel) of the Singapore Shangri-La. I stayed there in May 2012. The rooms and bed are very comfortable, the lounge food and drink offerings are great, the pool area is fabulous and the location is very convenient, BUT what makes this better than all of the other luxury hotels is that they will wash and press all of your clothes free of charge (something I have never encountered in any luxury hotel (and I have stayed in many) anywhere in the world.