There is a LOT on the market in Marina Bay, everything from higher priced single family homes to small, inexpensive condos. So the answer is "it depends". The higher end units have lost value, but at a smaller percentage than the less expensive one. Just last week, there was an auction to sell off many of these lower priced condos. You should expect that this auction attracted lots of investors, so many of these units will become rentals.
That being said, Marina Bay is a great location. The homes on the water are lovely, and many of the condos have great views. My opnion is that this will always be an attractive area in which to live, but for the short term, it may be difficult to sell homes there because of the glut. If you plan to buy and hold, then you should be able to get something at a great price today, and to sell it at a reasonable profit in a couple of years.
I've sold a few REO units at Marina Bay and have recommended it to several buyer clients both as an investment and as a great place to live. If I can be of further assistance then please visit me anytime at sfoluxury.com