I completely disagree with that statement, so YMMV.
I can think of a ton of cool things to do off the top of my head in Singapore--if you are into zoos and nature, the Singapore Zoo, Night Safari, Jurong Bird and Reptile Parks, and other nature reserves are great.
If you're a foodie, there are few places to get such a varied, cheap, and authentic taste of Asian food where it's completely safe to eat what you want, where you want.
Shopping is quite good.
Weather, while hot, usually offers you several hours of dry sunshine per day.
Nightlife is surprisingly good!
Day trip into Johor or Batam for some "international" flair.....
And more.

However, if it's your ONLY trip to Asia in your lifetime, then yes, I do agree to try some other parts of Asia that are more exotic (but also less clean, safe, reliable, etc). Singapore can be too "easy" and sterile--but for some, it's a nice intro to Asia.
But 5 days in Singapore? Easy! I've spent more several times, and always enjoy going back.

As for hotels, I second the recommendation of the Inter-Continental: Often there are room rates of S$160 for basic rooms, and the location is great, just above the Bugis subway stop, near good food and shopping too.

Have a great time on your trip!