atakam is correct. The Sheraton is not well located for the vast majority of travellers (you may be an exception) which is why there are no major hotels close by.

I lived in Singapore for many years and never went to anything near the Sheraton, and given the constant heat and humidity in Singapore, being close is great.

The Marriott, Hyatt, Hilton, Swissotel, Oriental, InterContinental, to name a few, are all better located with better access to MRT stations.

However I have been upgraded to the two-room suites at the Sheraton and in my experience the staff are familiar with the SPG program.