Depends which company does the survey, and where advertising dollars are best spent... QF think they have the title.
What are the world's safest airlines? - CNN.com
Now that QF "still call Dubai home", CX might be in with a chance at taking the top spot next year! How exciting! You could certainly do with some more banners to make Hello Kitty City Pretty!
I wonder how many different airlines have "Best Airline in the World" banners up at any one time during the year? A real competition worthy of note would be one voted by airline staff worldwide. Now that would be credible!