There are lots of great beer styles available right now, but you'd be forgiven for thinking it's all about imperial stouts. They count for 16 of the top 25 beers on beeradvocate.com and 17 of the top 25 at ratebeer.com.
The style originated in 18th-Century England, reputedly as a gift to the court of Catherine the Great—hence its original name, Russian Imperial. In recent decades American brewers have been crafting their own version, often called "double imperial." Confusingly, the newer, American style is often called simply "imperial stout." Take that, Anglo-Russian Entente.
Both styles pour like motor oil; they're high in alcohol, between 7 percent and 12 percent, with strong chocolate and malt notes. But Rocky Balboa would be proud: American doubles are even bigger than Russians—they're sweeter, more alcoholic, and much hoppier. And many American doubles bring a little something extra to the table: they're often aged, sometimes with vanilla beans, sometimes in whiskey barrels. Other times, they're brewed with coffee.
Imperial stouts are about as far from pale lagers as you can get. Which, in fact, may explain their popularity. They're the crowd-pleasing Cabernets of the beer world—heavy, boozy quaffs with popular flavors like chocolate, caramel, and spice. Think German chocolate cake in a bottle, doused in alcohol. High-alcohol beers of all kinds are hot right now, and the popularity of imperial stouts may come partly from the fact that, at 10 percent alcohol by volume or higher, all those flavors are needed for balance.