Actually, many historians agree that Hitler had several chances to win the war if he hadn't made several key errors.
For instance, when Japan attacked the US, Hitler immediately declared war on us. This was a mistake since it gave Roosevelt the ability to combat Germany directly (As opposed to simply supplying England and Russia through the lend/lease program) without having to wait for congress to declare war on Germany. Also, if Hitler had invaded Russia from the west with cooperation from Japan invading in the east, he would have most likely conquered Russia, and would have control of their war materials.