They're pretty much complete opposites. Greene's win was through no action of his own, it was just a complete fluke. O'Donnell whipped up a right-wing frenzy over Castle's moderate hero image and rode it to a primary victory. Greene didn't raise any money off of easily-duped left-wingers the way O'Donnell did with the tea party types. O'Donnell had a long history of making crazy statements in the media, Greene was just some crazy/mentally deficient guy who came out of nowhere.
There was still "DeMint started the recession." I want to make a bumper sticker of that...