IMHO is that George C. Marshall, Chairman of the Joint Chiefs of Staff, as THE best general in the war. His admistrative ability makes hime the greatest ever in WWII. The following are the reasons:
1. Who appointed Ike over a lot of other qualified, decorated, and out ranking generals?
Marshall did
2. Who appointed Nimitiz to command after PH?
Marshall did
3. Who conivinced Ike to return Patton to his command after the solder slapping incident?
Marshall did
4. Who made the outline for the midway plan?
Marshall did
5. Who empowered Ike to act as he saw fit during such crisis as the Battle of the Bulge?
Marshall did
6. Who was able to organize an under mobilized country to defeat the 2 most powerful nations other than the USSR?
Marshall did
These reasons alone are enough to put him in the spot of Best General. However if you need more I'll provide more but I'm kinda lazy and will provide more upon request.