I would have to give Rommel the number one spot for Germany with his brilliant panzer tactics and his actions in Italy which were hindered by Hitler's absurd orders. Number two for Germany would go to Manstein for attack plan of France and for saving Army Group South.. For the Americans Patton. In my opinion there aren't many other options which match up with Patton. Eisenhower, overated, Montgomery- what was with Market Garden??
the thing about montgomery was that he (helped) plan and command the normandy invasion and the arnhem attack. these two maneuvers are unmatched in size and audacity to this day. that's why monty got time magazine's vote for the century's best ground commander. normandy was spectacularly successful whereas arnhem was the basis for several airborne operations in vietnam, lat-am and the first gulf war. the other two best generals in the 20th were curtis lemay for strategic bombing and voh nguyen giap for guerrilla warfare.