Ah, that's so much fun. A politically incorrect post. :-)
German military forces participated "prominently" in both World Wars during the first half of the 20th century and stood watch with a larger ground force contingent than any other NATO power in Central Europe during most of the Cold War.There were many personalities among its generals that deserve to be known even long after their death - just as von Clausewitz the premier military philosoph, the army reformer Scharnhorst and Moltke the Elder during the 19th century or Frederick the Great during the 18th.
Thousands of German generals served during the 20th century, and I think at least five geniuses deserve a special mention here.
This is my chronological top five list
Bruchmüller actually never got past the rank of Oberst (colonel). He earned his nickname Durchbruchmüller (breakthrough Müller) by orchestrating innovative and hugely effective artillery support for offensives in the latter part of the First World War. He used an unparalleled knowledge of weapons and munitions effects to optimize the use of artillery and spent less ammunition for greater effect than the Allies did.
He was the father of modern artillery. He created an artillery paradigm that stood till the rise of precision guided artillery munitions during last years of the 20th century.
(2) Hans von Seeckt
He was an arch-conservative in his time and is therefore a politically incorrect choice, but he's more than notable for what he turned the inter-war army into: The most professional, most competent army of the world. The unbelievable growth potential and overqualification of that army enabled the impressive enlargement to the most powerful army of the world during only about seven years of the Hitler regime in the 30's.
The restrictions imposed on the Reichswehr during Seeckt's time in office dwarf any budget crunches that NATO armies ever suffered.
His approach of a ridiculously overqualified and professional army is still a worthy object for modern study. The Reichswehr was one of the few historical armies that didn't get fat, lazy and soft during peacetime.
(3) Heinz Guderian
The inventor of the most successful mechanization approach (Blitzkrieg) and a highly successful leader in wartime.
Liddel-Hart, Fuller, Tukachevski and de Gaulle were mechanization pioneers as well, but none of them developed an as revolutionary or as successful system as did Guderian (in concert with Manstein).
He deserved to be called the father of modern armoured warfare (with the exception of assault gun tactics).
(4) Erich von Manstein (born as Fritz Erich von Lewinski)
He was already known to be an operational prodigy during the late 30's and became the operational genius of the Second World War.
His operational concept defeated the supposedly most (or second-most) powerful army of the World (the French one) in six days* followed by less than six weeks of making it obvious for everyone.
He shattered the paradigm of secured flanks in conjunction with Guderian during 1940. This released the mechanised/motorised forces' mobility for full operational exploitation.
Likewise, he pioneered the operational concept of Schlagen aus der Nachhand ("mobile defense") later on the Eastern Front; he allowed Soviet forces to advance deeply, overextend themselves beyond the culminating point and cut them off with a flank attack. It was just as the 1940 operation against France a very daring move, one that required great patience and a victory over the fear that a successful enemy advance instills in soldiers.
I'm spoilt for choice. Any suggestions?
Oskar von Hutier, probably the father of modern infantry, was certainly a top ten candidate, but I'm not sure about top 5 status because the achievements that English-speaking scholars tend to attribute to him were apparently more an almost army-wide parallel invention.
(Forget about Rommel; he was more a talented self-promoter like MacArthur and Petraeus than a military genius. The German army had dozens of equal or better officers during WW2.)
It's politically incorrect in modern Germany to praise the talent and performance of German officers who were active between the end of the First World War and the end of the Second World War.
Nevertheless, these (three) stood out so much that they should inspire the present and coming generations of German officers to be as innovative and to help as talented comrades to succeed.
*: The French army commander Gamelin admitted on May 15th in presence of the American ambassador that they had already lost.