Good to see a candidate proposed outside the usual limited classical history and or Western perspective.
To which I’d add Yamashita in Malaya, whose reconnaissance, planning, marshalling and landing of troops, and subsequent campaign were masterly, pretty much faultless and overwhelmingly successful. He must be one of very few commanders who rejected the offer of substantially more troops to achieve his aim.
Slim is largely overlooked in WWII beyond those who know how well he did. More people probably know of Stilwell who, though a good fighting general but an appalling diplomat in dealing with the Chinese, did rather less than Slim in ejecting the Japanese from Burma.
At a smaller than Alexander etc but in my view more impressive level is U.S Gen. Robert Eichelberger who, as I’ve mentioned in various threads, was put in command of a division which had stalled and pretty much fallen apart in the field in Papua and, without the luxury of rebuilding it in a base with imported officers and NCOs and better conditions or any of the other things which convert a dying unit into a fighting unit, in short time in the field while facing the enemy he converted it into an effective fighting unit which then defeated the enemy it could barely face before he arrived.
For a consideration of whether or not Eichelberger was a military genius (=probably was, but open to debate) see the very slow to load paper http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA428623