I have to disagree with that. Genuinely good vietnamese, thai or even japanese food is pretty hard to find in singapore, and believe me I tried. Its specialities are dictated by its influences - southern china, malaysia of course, india, to some extent indonesia. The rest is decent of course but I just don't think there's an adequate population of, say, vietnamese in the city to sustain a general standard of quality comparable to what's available back home. Just try and find a good pork Banh Mi in singapore, I dare you.
If I had to name the city with the best general variety and everyday average standard of asian food - believe it or not I'd probably say Sydney.