I would suggest you read 'Colossal Cracks' if you can. Unlike the Germans or Americans, Montgomery had to fight a war under several constrictions. Britain had to conserve manpower, she could not just recklessly throw away the lives of the soldiers of the Dominions and Empire since they held the right to refuse orders and request advice from their own parliaments. Montgomery cared about his men, and had to ensure Britain had an army at the end of the war to play post-war politics. The view that Montgomery was just a cautious leader who used overwhelming numbers, is the opinion of outdated historians.
While my knowledge of the Battle of France is limited, my understanding is that Montgomery showed himself to be a more than competent general officer. In Britain, he revolutionized the training of men and demonstrated himself to be an excellent leader.
In North Africa, he demonstrated he was a superior general to Rommel. Rommel had showed, each time he had launched an offensive, that he did not appreciate the importance of logistics (his initial advance in 1941 left Tobruk in Allied hands and he outran his supply line thus handing over the initiative to the British. In 1942, after heavily defeating the British at Gazala he outran his supply line and was thus pretty much stuck at el Alamein). Historians generally agree that Rommel was an excellent divisional leader, but he should never have risen above Corps leader and he made numerous major mistakes in Africa. Montgomery seized upon the major efforts that the British had taken during the previous years to ensure that his logistical supply line would take him all the way to Tunisia. Unlike his predecessors he ensured his forces did not overstretch themselves, that had resulted in so much back and forth fighting. Rommel demonstrated that when the British overstretched themselves, he could launch counterattacks that would 'reset' the entire campaign. The advance that took place ensured victory and no setbacks.
I have to skip over Operation Husky and Italy, due to my limited knowledge of the campaign.
He played a key role in the planning of Operation Overlord, and commanded the ground forces throughout. The allied forces defeated Germany and advanced through France and Belgium at near enough the same speed the Germans had several years before, although they now had to face numerous technological advances. During Normandy, he launched numerous offensives designed to keep the Germans off balance and to keep German forces pinned down away from the intended breakout zone. While the battle did not go - letter for letter - according to plan, it was extremely successful.
Guderian favored concentration of force, breakthrough, and encirclements. So did Montgomery. His operations in Normandy show this, and his post-Normandy suggestions for a single thrust into Germany highlight this. Market-Garden, while it had numerous flaws, show innovation on his part and attempt to utilize everything at his disposal. There is more to its failure than just Monty's planning, likewise for the delay on tackling Antwerp. Market-Garden highlights a dammed if you do, dammed if you don't attitude some show towards Monty.
One historian noted how Patton, regardless of common perception, was very much like Monty. He highlighted how he ensured he had superior numbers, built up his supply train, had enough supplies for the operations, made heavy use of artillery, and planned heavily for operations. Peter Allen argued the operations Patton conducted in crossing the Rhine were very "Monty-esc".
Monty was one of the best generals Britain had to offer. He was a very flawed character. He lacked tact with people. He was loyal. He did what he had to do to ensure Britain fought a successful war and that Britain had an army at the end of it so they could play a political role.
Edit: "Goodwood was a failure". No it wasn't. It was a strategic success. The operation did largely what it intended to do: pin the Germans down, although territorial it did not achieve all of its objectives. The tank losses have been overplayed, and modern research have showed them to be very minor. Reading the primary sources show that the tank losses were replaced within days. It pinned down German forces when it was important to do so, and Cobra was supposed to be launched while it was underway. For numerous reasons, Cobra was delayed thus Goodwood was not launched in the context of what it was designed.