Our Great President, Lincoln, Washington, Reagan, etc. Are they great because of the decisions they've made or because of the timing of their Presidency?
Let's take the example of Lincoln. In the Gettysburg Address he didn't incite the troops to press forward and crush the South, instead he almost offered a truce. But what if he DID give a regular military speech and rallied the troops to crush the South? We would probably go down a different path in history, but in that path, will Lincoln be any less great?
Let's say he didn't issue the Emancipation Proclamation. Instead he negotiated a compromise with the South to allow slavery to continue with certain conditions. Would he be remembered as the Great Negotiator who ended the Civil War?
My point is Lincoln is remember now as the man who won the Civil War and who ended slavery. Based on that, people also studied his life and how he dealt with his friends and foes and tell other stories to support how great he is. But if he were to make completely different decisions which take us down a completely different path in history, will he still be remember a great President? If we were to put someone like George W. Bush as President of the Union will he be remember as a great President regardless of his decisions provided that they are somewhat reasonable and that the Union won the war?