Even the SQ cabin crew know which airport catering is better and SIN isn't one of them! I've had a comparison of regional airports for years and I've concluded that SIN's catering by SATS isn't great. Good catering choices are flights (any) departing from KUL, BKK and HKG !
But having said that I find that 'local' ie asian dishes are better prepared in SIN than say LHR !
I've ordered the Singapore Chicken Rice and that's always good, as well as the Thai Fish Souffle dishes. I would highly recommend the Oriental Vegetarian for people who are vegetarians (or not).. Its not BTC, but as a special meal.