1) MacArthur attacked the Bonus marchers apparently against Presidential orders.
2) MacArthur botched the training and preparation of the Phillipine Army.
3) Then AFTER HE HEARD ABOUT PEARL HARBOR he allowed his entire air force to be destroyed on the ground. He then apparently underwent a nervous breakdown (similar to Stalin after the German invasion) for a few days.
4) He then botched the defense of Luzon, attempting to fight mobile battles in Northern Luzon that ended disastrously.
5) His operations in New Guinea advancing to the Phillipines were largely the work of brilliant subordinates like Eichelberger, Krueger and Kenney. He was careful to make sure none of them got any publicity and credit. He even put Eichelberger on the shelf for a year because he still managed to get some favorable publicity.
6) The Inchon operation was a bit less impressive than portrayed. By the time it happened the Pusan Perimeter had already been heavily reinforced and the North Koreans would have collapsed anyway.
7) He utterly misread Chinese intentions in Korea and was yet again completely surprised by their attack.
This is not the record of one of the greatest generals in history.
MacArthur simply looked like a general, and had good PR. And much of his legend was politically derived (A hero of the Republican Party, who were desperate to get him to run for President...a job in which he would have been a disaster. Fortunately they turned to Eisenhower.)
He was a colonel at that time, not a general.