It's Miley!  (like duh).  Ha!  

This year, Cyrus was an easy choice, said Amy Doyle, head of MTV's music and talent programming strategy.

MTV said Monday the VMA duet on "We Can't Stop" and "Blurred Lines" was the year's most watched video on its websites. And Miley had more visits than any other artist's on her artist site (based on mtv.com). 

So wo decided this?  It's MTV executives who pick their choice for top artist. (One Direction won last year, and Katy Perry won the year before).