Quote Originally Posted by Pannonian
He fought in a strategically irrelevant area, where it didn't really matter what the result of the campaigns were, beyond mild irritation for the British. The European theatres and the Dardanelles was where the war was won or lost. Similarly, the middle eastern campaign helped cause the collapse of the Ottoman empire, but Russia had been eliminated by that time, and the main Axis protagonist Germany was relatively unaffected by its result (the Brusilov offensive causing the effective elimination of Austria-Hungary was more significant).

Among WW1 generals, I would go for AA Brusilov, whose infiltration tactics were said to have helped inspire the stormtrooper tactic later used in 1918.
1) The Dardanelles campaign was a publicity stunt, and a disastrous one at that. ANZAC, composed of arguably the greatest individual soldiers in the world, was a potential trump card that was simply thrown away, and fleet-overstretching by adding another front was the last thing the Allies' naval forces needed. Knocking out the Ottoman Empire was irrelevant because it was ultimately a paper tiger. The war could be won only on the Continent, and after Russia was stopped in its tracks only on the Western Front...

2) Lettow-Vorbeck kept at least 150,000 British Empire soldiers away from the Western Front. In the human-wave grinders that were Great War battles, those 150,000 could well have made the difference, in any number of ways. The fact that he fought in, as you say, a "strategically irrelevant area" makes his ability to cause the British to use so many resources against him only makes him more, not less, outstanding.

And its the Central Powers, not the Axis.