I've crewed for two airlines and have been an SLF on many. Singapore Airlines has the best service in my opinion (no bias I have never worked for them). Emirates I believe did and still has excellent service albeit inconsistent depending on the route but this has always been the case.
I must agree with a lot of the comments though because I'm sure this is what the original poster really wanted to hear - and that is who has the fittest attendants? Simple no contest - Virgin. bias? hell yeah!