Was James Buchanan a good president? Why or why not?

The general consensus among historians is that James Buchanan was indeed a bad president. The main reason for this assessment is that he did nothing to stop the drift of the United States towards civil war; if anything, he accelerated it. His wholehearted endorsement of the notorious Dred Scott judgement and his support for the pro-slavery Lecompton Constitution of Kansas are simply the two most obvious examples of Buchanan making a bad situation a whole lot worse.
Some historians have accused Buchanan of inaction and indecisiveness, of failing to make a firm stand either for or against secession. Others have been even less charitable, accusing him not of failing to take a stand but of taking the wrong stand, a stand in favor of the Southern states. As evidence, they cite his final address to Congress, where he heaped all the blame for the rapidly deteriorating political crisis on Northern opponents of slavery, accusing them of interfering with the rights of the Southern states.
Such blatant partiality towards the South was fairly typical of Buchanan's general attitude. He had, after all, been elected president mainly on the back of Southern votes, but what the United States needed at this crucial turning-point in its history was a spirit of bipartisanship from its president. Instead, Buchanan provided blatant pro-Southern bias. Instead of rising to the challenge of his time and providing much-needed leadership when it was most needed, Buchanan chose to ignore the many problems caused by the issue of slavery, thus virtually guaranteeing civil war.