Branding is the single biggest defense against any incumbent. Universally agreed, branding is a very strong defense.
They had sales of 150 Million. Merely six times? Consider that against some Bay Area startups valuation !!
As someone who aced the Pepsi Challenge when they were around, they have very different tastes (I don't like the way Pepsi tastes at all), and I'm not the only one.
In fact, the Pepsi Challenge existed solely because Pepsi thought theirs tasted so differently.
Who are they getting to do these blind tests? Coke, Pepsi, and RC cola have distinct flavors -- the generics do too, although I don't have enough experience to identify them. Cans, bottles, and fountains don't taste the same either. Branding and affinity certainly influence which vendor is preferred, but the drinks are not the same.