Even so, he's not THAT overrated, after all, he may have failed to break out of Normandy ahead of Patton or Bradley, but he was facing 3 times the number of tanks the american forces were, plus the whole point of that campaign was that he was to pin the Germans in place whilst the Americans broke out and surrounded them, you can't fault him for doing the role he was intended for. Naturally his attempts to break out were bad, but it's hardly fair to judge him in comparison to the US commanders when he faced so much more problems than they.
Arnhem you can fault him for, he should have stopped that before it even started and recognised that the plan was madness. But overall, whilst I would not say he's the greatest commander, he did have considerable ability, to say he's overated is unfair to the situations he faced. Since I don't think many consider him the greatest general ever, and most simply rate him as "good" that is hardly overating him.
As for Normandy landings, at least he had control over the British beaches, which if they did not complete his over-confident objectives, at least they had more sucess than the American beaches alongside them. Planning or not, the British and Canadian beaches were secured quicker than Omaha for example.