Consumer Reports' testers deem McDonald's coffee better than Starbucks, giving McD's brew a "decent", while Starbucks got a "burnt and bitter". Not a surprise that Starbucks has the nickname of "Charbucks" in these parts.
I had a guy tell me once that the reason that Starbucks was so popular was because of the quality of their coffee. Bullcrap. They sell ambiance and atmosphere, and have elevated a beverage to a status symbol. That, and familiarity and marketing, is why people buy Starbucks' coffee, not because of its quality.