Yes, maybe even a military masterpiece. However, the decition to start the war was a big mistake. Hitler's calculation that France and GB wouldn't go to war was wrong. So what I am trying to say is that even though this campaign was won the war was lost. There is no szenario how Germany could have won the war. Norway, France were other big victories and did improve the position of Germany. But Hitler was not able to end the war. And there was no realistic plan to end the war after that.
What do you do if your enemy won't accept a peace and you cannot force him? A good General/politician doesn't start a war if he has not at least knows how to end it.
At Stalingrad the war was already lost, Hitler may not have realized it. Even if Hitler had won the battle of Moscow, would that have changed things? I do not think so. And if he hadn't attacked the USSR at all. Well, sooner or later Stalin would have. And if he had won the battle of England? German fighters did not have had a realistic chance to win this battle. Even if their commanders hadn't made such terrible mistakes. But let's assume they won and Germany invaded the island successfully. So what? Would that had stopped the war? I doubt this.
No, Poland was the mistake!