Equally or even less generously, climate denier/coal magnate David Koch said Obama "didn't contribute much at all."
Moving beyond these in-depth analyses, is there any fair way to analyze it? We could try by assigning credit and blame before you know the outcome, as in what I wrote on January 22:
With exactly two years since Obama's inauguration having passed, I'm somewhat arbitrarily picking this as the time where his administration bears greater responsibility for anything done well or poorly by the executive branch than any previous administration. Credit and blame can be adjusted on a case by case basis - for example, Bush bears more responsibility for 9/11 than Clinton because he downgraded counter-terrorism efforts - but as a general matter this makes some sense to me.
Of course, the president with the next most responsibility is Bush, without adjusting on a case by case basis.
So on with the adjustments! For Bush, we have screwing up Tora Bora by not committing enough troops and trusting allies he shouldn't have, and generally pulling CIA assets out of Afghanistan and into Iraq, and the small matter of his share of blame for letting 9/11 happen at all. To Bush's credit, there's eventually relying on the patient intelligence gathering game that Obama continued through another 2-plus years.
Obama gets credit for warning in the campaign that he would go after Osama in Pakistan, despite criticism from McCain and Hilary. Obama also gets credit for a manned ops instead of bombs. Bombs may have killed Osama just as well, but there'd be no body, no intel from captured material, much more collateral damage, and massive outrage from Pakistan unleavened with the current mix of outrage plus embarrassment. And Obama reconstituted the CIA bin Laden unit that Bush had demobilized.
Finally, we've got torture. Bushies like to point out that the people they had tortured gave the initial intel that eventually led to Osama. Far fewer of them realize that the captives held out during the torture sessions and only gave up the info months later during standard interrogations. I don't think this particular set of info is entirely clear, but I'd tend to score it against Bush and the pro-torture wing of the Republican Party.
I won't attempt to make a definitive adjustment for the credit game, but qualitatively I'd start off with my initial preponderant share of credit to Obama, adjust upward for his decisions, and mostly adjust downward for Bush's choices.
David Koch, in the end, can add one more facet to his denialism.