Well lets see.. Monty was only half heartedly successful if the Americans threw supplies at him, which history states he was quite free with. Americans lost tons of men on ships keeping his "El Alamein" walk across North African chasing the starving, ill supplied Germans alive.
He took the easiest routes in Sicily and bitched because Patton got to Messina first (not a big Patton fan either). Talked Eisenhower into giving him the least bloody beaches during D-Day (much respect for the British commandos though) Had almost every action covered by *huge* American 8th Army bombardments.
Lets just Market Garden was a grab for glory that didn't work out. He left the Americans to fight through Montecasino to create a new front at Churchill's request.
As a strategist, he was below average in my eyes. He relied on "expendable" foreign troops. Americans regard him generally as though he thought Americans were fine fodder for the cannon, but not for much else.
I think Patton was a primadonna as well, but at least he understood history, and was willing to research situations before running headlong into it...
And yes, his slowness squandered advantages, resources, and lives.