Three presidents gather for Bush portrait unveiling NEW: Former President Bush and his wife unveil their White House portraits NEW: The Obamas thank the Bushes for helping smooth the transition NEW: Bush jokes that now Obama can ask: "What would George do?" Washington (CNN) -- There were smiles, laughter and tears -- but little politics -- when former Presidents George W. Bush and his father, George H. W. Bush, joined current President Barack Obama at the White House for the unveiling Thursday of the younger Bush's official portrait. An emotional ceremony in the East Room saw the new White House residents thanking their predecessors for their service to the nation and for helping them out during the move more than three years ago. In personal tributes to the 43rd president and his wife, Laura, both Obama and the first lady expressed their appreciation for the example set by the Bush family during their eight years in the White House and the guidance and help provided during the transition. "George, you went out of your way, to make sure the transition to new administration was as seamless as possible," Obama said, adding: "I'll always be grateful for that." He also cited Bush's strength and resolve that reassured the nation after the September 11 terrorist attacks, and made sure to note that anti-terrorism efforts started in the Bush administration helped bring the signature national security achievement of Obama's presidency so far -- the killing of Osama bin Laden. The tone was markedly different from Obama's campaign themes that blame the Bush administration for leaving the nation in economic shambles. However, Obama mentioned the economic turmoil at the time of the transition, saying that was a reason he especially appreciated Bush's efforts to help make it as smooth as possible. "After three-and-a-half years in office and more gray hair, I have a deeper understanding of the challenges faced by the men before me, including President Bush," Obama said, adding that one truth is you can't make everybody happy. "I think that's something President Bush and I learned pretty quickly," Obama continued, later noting that "we may have our differences politically, but the presidency transcends those differences." Both Bush and Mrs. Bush, who also had her official portrait unveiled, thanked the Obamas for their hospitality in hosting the event that included lunch with the Bush family -- including both former presidents and first ladies as well as former first daughters Jenna and Barbara. They also made a point of thanking the White House and administration staff during their eight years in Washington, and cracked jokes that caused the packed East Room to erupt in laughter. "Thank you so much for inviting our rowdy friends to my hanging," Bush said after shouting "sit down" to cut off a lengthy standing ovation when it was his turn to speak. Bush quipped that he hoped the president will find reassurance because, when walking the White House halls at night mulling over a major problem, "you'll now be able to gaze at this portrait and ask 'What would George do?' " Mrs. Bush also drew a big laugh when she said in reference to the new paintings that "nothing makes a house a home like having portraits of its former occupants staring down at you." In the most emotional moment, Bush's voice cracked a little as he said of his father -- the nation's 41st president -- that he was honored the portrait would be "hanging near a man who gave me the greatest gift possible, unconditional love, and that would be No. When Michelle Obama rose to speak, she began by saying: "I don't think we have enough tissue to go around." "Jenna and Barbara, they're just a mess," she added in reference to the Bush daughters. The Obamas made a point of thanking the Bush girls for guidance they provided the Obama daughters, with Obama noting his two girls have followed the advice to make loyal friends and slide down the bannisters. The portraits by John Howard Sanden show Bush standing in the Oval Office, while Mrs. Bush, wearing a midnight blue gown, is in the Green Room that she helped refurbish.