As compiled by Pitchfork. While I’m not all that familiar with the work of the Seattle based Fleet Foxes, who top the 2008 list, this summarisation is somewhat persuasive:

They’re like two sides of a coin, and equally express the band’s mastery of its music, a catchall Americana that takes a wide slice of our popular music’s spectrum and pulls it through a reverse prism to create a gorgeous and focused sound of the band’s own. The threads of Brian Wilson’s intricate coastal pop, Appalachian folk, modern indie rock, Grateful Dead jams, and other influences are masterfully synthesized in the band’s harmonies and simply orchestrated but constantly shifting instrumental arrangements.