If your are flying first or business class than these three are the best. If you are flying coach all airlines are pretty much the same. The exception to the rule is if you are able to fly the one A380-800 on Singapore Airlines which has about 10 rows of coach on the upper deck level. I think they have only one in their fleet with this configuration.

That was truly an amazing coach experience. All the rest are like taking a flying bus. I will say that SIA in coach is like taking one of the luxury mass transit buses in Singapore.