Claim: The three most valuable brand names on earth are Marlboro, Coca Cola, and Budweiser, in that order.
Origins: The value of a recognized brand name is both difficult to estimate and difficult to overestimate. Certainly companies with long-established, widely-recognized brand names don't overestimate their value, spending millions of dollars in advertising every year not to directly promote sales of specific products, but simply to keep their brand names in front of the public. As for estimating and assigning a specific value to a given brand name, that's something an organization called Interbrand has been attempting to do for several years
now.
Interbrand assigns values to brand names based upon four criteria (too technical to go into here) and publishes an annual list of their brand name rankings. The brands they valuate must be worth more than $1 billion, they must be marketed globally, and they must make sufficient marketing and financial data about themselves publicly available. (Brands such as VISA and Mars don't qualify because their financial data are not publicly available). Companies which manage portfolios of brand names (such as Procter & Gamble) are ranked separately.
The widely-circulated bit of Internet trivia cited above — which claims "the three most valuable brand names on earth are Marlboro, Coca Cola, and Budweiser" — is based on an Interbrand survey, but it comes from an older survey which is now outdated. According to the 2002 rankings of the World's Most Valuable Brands, compiled by Interbrand and BusinessWeek magazine, Marlboro is no longer the #1 brand name, having tumbled to 9th place. Budweiser has fallen even farther, down to 24th place.
Coca-Cola is still going strong, however, holding down the #1 spot as the world's highest-ranked brand name in both 2001 and 2002, followed by Microsoft and IBM. Rounding out the top ten are (in order) General Electric, Intel, Nokia, Disney, McDonald's, Marlboro, and Mercedes.