GHWB's greatest success was his handling of the end of the Cold War IMO. More than anything, that was his greatest success. (and it was huge)
As for Obama, killing the US's single most wanted foreign adversary and the decimation of his organization definitely counts as foreign policy. He's also strengthened the coalition against Iran's nuclear program, leading to a significant improvement in one of the US's thorniest foreign policy problems, his intervention in Libya was largely successful, etc, etc.
It's not that he hasn't had blunders (Syria clearly comes to mind), but overall he's done a good job. Compared to his predecessor he's practically the second coming of FDR.
Sure, he's decimated Al Queda, so much in fact that they didn't just retake Falluja and are not becoming the defacto leaders of the Syran insurgency...
And absolutely he has strengthened our coalition against the Iranian nuclear program. Our coalition is strengthened by alienating Israel and Saudi Arabia. All hail Dear Leader!