Obama has been in the White House during a recovery from a deep recession while George W. Bush has lead a recession free country most of his time in the White House (recession began in 2007). Maybe it runs in the family since George H.W. Bush didn't encounter a major recession as well?
Then again the debt of US might have more to do with major wars that the US has held. War on terrorism began in 2001 after 9/11 and has cost more than 3 trillion to date (as is been estimated by various sources). At the same time there were no major extremely expensive wars held during the eighties or the nineties. At least their costs don't reach to anywhere near of the Vietnamese war or the invasion of Iraq and Afghanistan during the previous decade.
All in all the presidents that the US citizens can be "grateful" for their massive debt load involve most importantly the Bush family and Ronald Reagan. What do you think?