Wikipedia (I know its not guaranteed) has
SQ21 EWR-SIN 18hrs 40min on 29-06-04 (8963nm)
EK215 DXB-LAX 16hrs 35min on 26-10-08 (7246nm) (start date)
If this info is correct Emirates doesn't even come close.
Next time I'm onboard I'll try to get the Great Circle distances from our nav kit. Not sure if our database has all these places as we only fly Europe and Middle East,
Fly safe.