Like OP mentioned, Singapore airlines without a doubt. Qatar would be my second choice as well. I did the EWR-SIN 18 hr flight in 2005 when it had economy class as well. Even economy didnt seem that tiring....despite me working for a a good 14 hour period during the flight. Besides, the FAs came to know that it was my birthday (maybe the gate agent noticed it in my passport) and they made me cut a special cheese cake mid-flight and offered it to fellow passengers.