You can restrict YouTube's search results to feature length videos by appending &longform=1:
http://www.youtube.com/results?search_query=site:youtube.com&longform=1
It's not clear how YouTube filters feature length videos, but most of them are from the Authors@Google series, Standford University, Carnegie Mellon University and Vancouver Film Studios.
If you want a YouTube interface that looks more like Google Video, try the YouTube Googler Greasemonkey script.
{ Thanks, Daniel. }