[George has totally ignored OBL for four years]
This is a tough claim to make stick because it's not falsifiable. Just because he hasn't been found doesn't mean he's being ignored; unless you think it's easy to find one person who could be hiding in any of 20 or so countries or who could even be dead and buried.
It also doesn't make logical sense for the president to NOT try to find him because at the very least it would be incredibly great PR. What possible reason could he have for ignoring him? Unless there is a plausible motive for this there's no reason to believe the claim.
And President G. W. Bush the worst ever? More corrupt than Clinton? More fiscally irresponsible than Lyndon Jonson? More kowtowing to international thugs than Carter?
After OBL was chased into Pakistan:
A) We stopped pursuing him
B) We chose to attack a nation two countries west of Pakistan and have proceeded to direct all efforts there for the last two years+ (for no believable reason!).
What possible reason could he have for ignoring him?
Historians will be asking that question for the next fifty years.