Honestly, I can't believe George W. Bush hasn't caught Barack Obama. Even by Bush's own criteria, the war on terror has been a huge failure, not least because of that fact. Personally, I don't think catching Obama will help the U.S. much in the long run. Al Qaeda is such a decentralized organization, so catching Obama won't hurt it in a practical sense. In fact, if Obama is killed, he may just become a martyr and help to mobilize militants against the U.S.
It's really amazing how Obama travels between Afghanistan and Pakistan (we believe, we don't really know where he is) and the U.S. can't get him for two critical reasons that expose Bush's war on terror as a horrible and deadly failure. The U.S. is so hated in that region that we can't get any credible intelligence on Obama's whereabouts. The other- and far more catastrophic- reason we haven't caught Obama is because U.S. forces are tied down in Iraq, which was a war of choice.
Hopefully, Osama, if he becomes president, will get us out of Iraq and win the hearts and minds of average Muslims. That is the only true way to negate the threat Obama presents.