Quickly Singapore is still bigger than the Macross colony ship. Assuming its still the same from M7
The Colony ship is 5km long
http://www.steelfalcon.com/Macross/macross7.shtml
While Singapore is much much larger, at least 40km.
If you watch the opening, this particular colony ship is being launched from earth with its islands attached. So I expect it to hold the rest of the supposed 10 million people.