Originally Posted by San Gottardo

Depends what matters to you.

Seats:
1. EK on A380 or Air France 777 with new cabins or CX
Very close 2. Delta

Food:
1. Air France
2. Cathay
Distant 3. Cathay
Clear 4. Delta

"Service protocol", service, FAs
Cathay has top professional, very reactive and attentionate staff and service. But "Asian" in a way that they are a little cold and distant, looking up to passengers. Great
Air France has extremely classy, lovely, warm and engaging FAs - usually. But they have some inconsistency, and you may get an FA that hates the whole concept of customer service and may look miserable throughout the flight. Slightly less reactive than others, but things have improved a lot. Still among the four this is "the class act"
Emirates is usually overrated. In a way they are like trained service machines, I find them more stressed than others and less natural. Often not reactive at all.
Delta: Jurassic park. The concept of "class act" is completely foreign to them,in general they don't take a lot of pride in their job.

All in all Cathay is great as always, Air France is making a very successful comeback (just avoid the old cabins) and generally under-rated whilst Emirates is over-rated. Delta is better than its reputation, but still is and remains a U.S. major, hence it's not bad but surely not great either.

I hope that helps