It’s important to remember that Starbucks is everywhere, so there are some regional preferences when it comes to the most popular drinks. For instance, polls have shown that the Frappuccino is popular in California while espresso is the drink of choice up to the coast in Seattle. Iced lattes are preferred in the South and, quite appropriately, warm lattes are hotter in the North.
Starbucks is also a worldwide chain of coffee houses and the menus do change from country to country. Each country also has their own preferences.
In Italy, espresso is typically considered to be the best coffee drink, while in France, cafè au lait is more popular. These are general preferences for coffee and are not exclusive to Starbucks. Depending on where you live, there will be new favorites.