Hitler wasn't a military genius. He was possibly an "inspired amateur", and in certain cases he did spot solutions that his Generals working from a narrower military frame of mind would not consider (his decision to defeat the Red Army at Kiev and seize Eastern Ukraine before turning on Moscow in 1941 is the first one that comes to mind), but it is quite a step to call him a military genius.

Memes to the contrary, the German Army did not invade France in 1940 with the Schlieffen Plan Redux, nor was the French Army so obliging (or cowardly, depending on how inaccurate the meme is) as to forget to defend Belgium. In 1940, the German General Staff led by General Franz Halder was deeply unhappy with the prospect of a war in the west against France and Britain. All of these men had fought in the First World War, and they remembered well the failure to break through in France, the slow attrition of the German Army, and the Royal Navy's blockade slowly starving the population at home and robbing it of its will to fight. The first plan Halder presented to Hitler has been called the "Son of the Schlieffen Plan": it was essentially a repeat of the 1914 plan and envisioned a massive smash through central Belgium, sacrificing half-a-million men just to get to the line of the River Somme, at which point Germany would be unable to resume the offensive until 1942. Hitler predictably found this plan unacceptable. Subsequent revisions did not fundamentally change Halder's plan but included an attack on the neutral Netherlands and a secondary attack through the Ardennes region.

The expected Franco-British response was a counter-invasion of Belgium with the best of the French and British armies to ensure that the bulk of the fighting stayed out of France proper. This was the point of the Maginot Line: having experienced the occupation and devastation of some of its richest agricultural and industrial territories in the First World War, the French were determined that they should never fight a war on their own soil again. The Maginot Line was intended to make the France-Germany border impassable and force the Germans to commit to an invasion of Belgium. The heaviest fighting was expected to take place in the Gembloux Gap in central Belgium, a relatively flat area of land between the Meuse and Dyle rivers that formed a natural invasion corridor and made excellent tank country. In the event, the French and British did exactly this in Plan D - advancing into Belgium after receiving word of the German invasion, they advanced to defend the river lines of the Meuse and Dyle as the Belgian Army retreated, and prepared to receive the German attack. Critically, the French Seventh Army had been removed from general reserve to cover the Allied left flank and move into the Netherlands to link up with the Dutch Army. This left no major mobile force in place that could be used to contain the German breakthrough in the Ardennes at Sedan.

There was pronounced internal debate within the German Army about the possibility of making the attack through the Ardennes the main effort: the commander of Army Group A, covering that area, Field Marshal Gerd von Rundstedt, and his chief of staff Erich von Manstein, argued that it presented the best opportunity of achieving a breakthrough at Sedan and outflanking the best of the French Army as it moved into Belgium. Other officers regarded the plan as insane, seeing it as throwing seven panzer divisions into an area that was difficult to supply and could easily be interdicted from the air. Halder even tried to banish Manstein to East Prussia to get him out of the way, but after much internal politicking, Hitler ordered Manstein's way of thinking to be adopted as it offered the best possibility of a decisive victory in what was an extremely gloomy strategic situation for Germany.

In summary, Hitler did not use the same First World War plan of invading France, except in the broadest possible terms of a violation of Belgian neutrality, which in both cases the Germans committed because the France-Germany border was heavily-fortified. However, the German main effort in 1940 was in the south through the Ardennes; in 1914 it was to the north through Brussels. A repeat of the 1914 plan was considered and rejected as unambitious and costly, while the plan that was adopted was largely the product of professional military officers to whom Hitler acted as a mediator.

Sources:

Lloyd Clark, Blitzkrieg: Myth, Reality, and Hitler's Lightning War: France 1940

Douglas C. Dildy, Fall Gelb 1940 (1): Panzer breakthrough in the West

Douglas C. Dildy, Fall Gelb 1940 (2): Airborne assault on the Low Countries

Robert Kirchubel, Atlas of the Blitzkrieg: 1939–41