It is a shame that SlideShare did not set a subject for the contest, this would level the playing field. Part of the competition now is to find a compelling story, many presenation design gurus are probably in writer's block as we speak.
The winner will be selected based on a professional jury, votes, and on the distribution of the presentation in social networks. So part of the effort is to design the content, part of the work of a contestant is to run an election campaign.
In the next edition SlideShare should run a finale similar to American Idol, in which the finalists have to present their slides in front of an audience/video camera.
I hope the winner of the contest will be a presentation that touches people, and makes them change their behavior in some way or another. This is not neccesarily the presentation with the most beautiful pictures, motion typography or amazing professionally crafted cartoon characters and sketches.