I was also raised to respect the President. The Kennedy assassination happened when I was seven, and that was a huge shock to my whole family. Even though my parents voted Republican they grieved for Kennedy. I can't honestly say that I think most Republicans would feel the same way if something happened (heaven forbid) to President Obama. There's a coldness and lack of love in the political atmosphere of the country today that I find disturbing. I remember the Nixon era and his scandal and resignation, and the fact that my dad didn't ever vote Republican again after that. But still we were taught to respect the presidency. Later, in my former career, it was a requirement of my job to respect the President, since I worked for the military.
So it's shocking to me how politics has morphed in recent years, to outright hatred expressed toward presidents. George W. Bush was my least favorite president of all, but I respected his position and I didn't like it when the criticism got too obscenely harsh, even when I honestly thought he should probably be impeached (still do). I still thought some of the public bashing of him was harsh and uncalled for. It was not just hateful toward him, it was also disrespectful of his position. I see no call for that kind of hatred.
The whole "birther" phenomenon and the outright hatred toward Obama, expressed sometimes for I can't fathom what reasons unless some of it is racial, is shocking to me as well. He's so centrist, I would think Republicans would prefer him over others he beat out, and after eight years of Bush/Cheney, I'm not at all surprised a Democrat was elected.
The two best presidents in my lifetime, in my opinion, are Eisenhower and Kennedy. From different parties but IMO equally deserving of respect. (I don't remember Eisenhower, I'm going on what little I've read about him since.) Obama and Clinton come in third and fourth for different reasons, though Clinton's personal escapades detracted from my respect for him (though they were unrelated to his work as President for the most part), and I also think he was more corporatist than he appeared. He balanced the budget, but I am not sure he can take full credit for that, either. Both Obama and Clinton are also too centrist for my liking.
Johnson would beat out Clinton in my estimation based on his support of civil rights and education, except that I find Johnson's decision to fund the Vietnam War rather than the War on Poverty pretty disappointing and something of a sell-out. All of these have their flaws, they have all been human and imperfect. They all made mistakes.
But when you look at that job, how many different interests and crises have had to be addressed, how much opposition each of them dealt with, and how much they aged while in office (those who survived), I can't say I can see any president as a total flop. It's a position that takes a lot of strength, endurance and energy to pull off. I know I couldn't do it!