FDR and Truman administrations cost millions of American lives via miscalculations in WWII and Korea. Eisenhower sent the first military advisors to Vietnam, Kennedy greatly escalated that effort and opened the door for greater US military involvement, Johnson moved us into full blown war that would cost more than 58,000 American lives, Nixon and Ford managed to disentangle us from that war but did so by abandoning our allies. Carter had the Iranian hostage situation to contend with. Reagan had the terrorist attack on our forces in Beirut. GHWB was successful with Desert Storm but has been criticized forever since for 'not finishing the job' when he could have. Clinton deal with multiple terrorist attacks including the World Trade Center, Oklahoma City, the Cole et al plus the terrible misfire in Somalia that saw the bodies of our Rangers dragged through the streets. The GW Bush Administration has accepted full responsibility and freely admits they misjudged Saddam's Republican Guard when they chose not to disarm them following our initial victory in Iraq. That same Republican Guard reformed into the insurgency that opened the door to infiltration of more terrorists. And Obama's military record? Not exactly stellar.
So criticism for everybody. But disqualifying if they don't get everything right? Then nobody is qualified.