If we're talking about US Presidents, I pick Clinton, with Bush sr. as a close second. Not sure about LBJ, though, I don't know enough about him. Maybe he gets honorable mention for the civil rights program.
Why? Kennedy is overrated and did not have the time to do anything extraordinary, although I really like his Berlin speech. Nixon disqualified himself with Watergate. I don't remember Ford doing anything extraordinary. And while I don't understand the bitter resentment towards Carter, and would not say he was such a bad President after all, he certainly wasn't very good either.
Reagan may be noteable for getting the economy up and running again, but was hardly the fiscal genious some paint him to be -- he too was into excessive spending next to the cutting. Also, Reagan was too deep into ugly Realpolitik excesses, such as Iran Contra and arming Saddam against Iran, arming the Taliban precursors in Afghanistan against the USSR, which created so much trouble later, which places him far, very far from the "best" label. Without Reagan's policies, Bush jr. wouldn't have had much to do, from 9/11 to Iraq. Reagan messed up, and Bush jr. later had to do the cleaning (and failed too).
Bush jr. was an abomination on all fields. He did severe damage to political discourse and political culture and failed on almost everything he did, leaving the country broken into pieces and deeply divided. He was the President of human right violations, trigger happy military adventures and economic suicide. Bush jr. played away the surplus he inherited from Clinton, totally in the pockets of big oil and weapon business. He probably was easily the worst of them all. Obama inherited the shattered pieces that once were a prospering country from Bush, restored some minimum of basic sanity, but beyond that, has not had a chance yet to prove how good he is. So let's wait and see how Obama will make in the next months or even next four years. He's still to fresh for a fair estimation.
This leaves Bush sr. and Clinton. I'm biased in favor of Bush sr., because he proved to be a good friend of my country, by supporting Germany in the exciting days between 11/9/89 and 10/3/1990, allowing a peaceful reunification. He also showed Saddam the limits, without screwing it up like his son did. And Clinton -- he's first, because there is not much bad that comes to mind when I think of him. Sure, the Lewinsky stuff, but I don't really care about that -- and he really did a very reasonable economic policy, leaving an almost balanced budget to Bush jr., who all played it away. Clinton was not a warmonger, but no wimp either, he pushed us Europeans to actions in case of humanitarian disasters such as the war in Yugoslavia, but not easy-handedly, but when all other options had failed.
So it's Clinton and Bush sr as close second.