Never been to S/E Asia.
Comparing Negril beach to any beach on the big island of Hawaii = Negril wins.

I will say this too, I don't come back to Negril strictly for the beach ( though it's a big plus), I come back for the entire Negril ambiance.
If there is one source for the ambiance I'd say it is the people of Negril.

PS don't overlook the west end