It's more likely that he is alive and being questioned by the US intelligence services. Had the US paraded him on TV for the worlds media, the resulting reprisal attacks from extremists would have been severe. Better to say he's dead than admit he's alive.
Also, if he really is dead, burying him at sea is the only way to ensure their isn't a physical location where people can mourn him. Even by burying him in secret there is a chance his body will be traced.
As for your ratings premise; the death of Bin Laden reinforces the bush doctrine and his war on terror. This goes some way towards providing justification for the war in Afghanistan. Whilst Obama may get a temporary gain in the polls, ultimately he along with the democrats who were against the war, will suffer politically.
What's more worrying having seen the pictures from outside the White House is the sentiment of the US public who see Al Qaeda's and terrorism's centre of mavity as Bin Laden himself. The comedian Rich Hall said it best when he called terrorism a franchise. Terrorism won't end with Bin Laden, despite the opinions of some Americans.