Sure, having a sandwich named after you at a deli is nice, but what better way of ensuring lasting fame than having a drink named after you? Not many people have that luck, alas -- at least for widely known drinks. There's Tom Collins, but he may or may not have been a real person. There's also the Martini, but there again the origins are hazy, as is often the case with alcohol-related matters.
What's the value of the PR reaped by Manhattan from the cocktail of the same name? Incalculable. I believe the opportunities for new, lasting cocktails are limited, however, because simpler is better. The proper Martini, without question, is gin -- of either the London or Dutch type -- and a few drops of vermouth.