A brand is a reputation your money makes, and Los Angeles is best in the world at turning money into things that look like respectability: in LA, money turns the same stale superhero story into seven varieties of blockbuster, it turns oppressive theocrats into purveyors of exclusive opulence, it turns foot-stomping and hand-waving into serious policy discussions, and of course it turns racist slobs into respectable businessmen and philanthropists. So obviously "a brand consultancy that prides itself on its expertise in urban branding" (via The Guardian) has found that Los Angeles has the best brand of any major city on earth.
Consultancy Saffron found Los Angeles does ok on "assets" ("attractions, climate, infrastructure [particularly transport], safety and economic prosperity") but terrific on "buzz" ("a combination of social media [Facebook likes and Twitter sentiment analysis] and media mentions") for a total combined score higher than New York, London, or Paris. But then, this list also ranks Las Vegas above Buenos Aires and Berlin, so whatever. Seriously, this is the insight level here: "All the European cities do relatively poorly, perhaps because there are so many crammed up against each other."