It's not because LeBron James sucks. It's because he's more of a power dunker and not a flashy dunker like Jordan and Kobe and DWade. Also because all the good dunks have been used and only guys like Nate Robinson and Gerald Green actually have the time to think up crazy dunks and win it. (Although Howard won it last year and one of the rarest occasions a big man has won it in the modern era, mostly its the guards.)