Well when talking about a 2 front war that didn't truly start until D-Day. He did attack all the nations around him. Some in example: Poland, France, Belgium, Luxembourg, Greece, etc. These nations hardly gave up a fight some only lasting at max of 17 days because it took that long for the Germans to walk across the country. But the thing that stopped Hitler from conquering all of Europe I think is Pearl Harbor. There is a rumor, that many historians think is true, that when Japan bombed Pearl Harbor he sent there emperor a telegram saying ARE YOU COMPLETELY MAD?!
Hitler could of handled a 2 front war if he had to, if USA didn't come in. I'm not saying that if USA never helped in WWII we would all be speaking German but they played a HUGE part in the western front. I do not think Hitler is a bad strategist, he was quite good. His ideas on politics and how he said what he would do in order before he actually came to power was amazing. If you don't believe me, read his book Mein Kampf
If Hitler had focused on the UK then Russia I think it would of been a different story of the war. He could of taken, like Snauhi said, the UK not with total easiness, but he would of had a easier chance of taking it instead of Russia.
I do not really know if he would have conquered europe/asia/world because he focused more on the bombings of civilian targets other than military. If I had been Hitler, scary thought :rambo: , I would of done as he did and taken over the easy nations around me. Then focused on UK. After taking UK, I would have my Allie, Japan, do as they did and invade China, but NOT bomb USA. Thats the thing that historians claim lost Hitler the war, not his "bad" strategy, but the "bad" strategy of the Japanese in that time. Well I don't want to keep rambling. All-in-all Hitler would not of taken over the world/europe if he had started bombing military targets other than civilian ones.