If Rolex is not the only superior watch brand, why haven't I heard of these other watches?
Popularity is only one indication of a superior product. In most cases, the general public knows only certain brands which were well publicized as the 'best of the best' and may be totally unaware of other equal or superior products that are available. If you asked the average person-on-the-street about watches, they would probably tell you the market starts with Timex and Casio, moves up to Seiko, then TAG, and reaches its epitome with Rolex.
Yet the most popular or well known choices frequently are not what the true aficionado would select. I'm sure you would find your man-on-the-street sample would also be unaware of the true collectors' choices of wines, cigars, audiophile equipment, sports cars, or writing instruments. Similarly, they will unlikely know the additional fine watch brands such as Alain Siberstein, Audemars Piguet, Blancpain, Chopard, Fortis, Franck Mueller, IWC, Jaeger-Le Coultre, Patek Phillipe, and Ulysse Nardin to name a few.
In many products, the well-known brands like Bose, MontBlanc, Sony, and Rolex dominate their markets from global name recognition. While they do have quality products, they are not always the only superior choice. Success can spoil the innovation, the competitive edge, and the uniqueness that was what built the reputation these companies and products enjoy today. Sure, if you want to impress the general public, you buy names anyone will recognize--sometimes even without regard to outrageous premium prices or quality and features that are less than one would expect from their "leader of the pack" reputation.
But the true connoisseurs and aficionados buy what impresses *them*, which may often include brands that the general population would not even recognize.