Honestly, I've thought about this a lot, and after watching a documentary on the History channel, it affected my views even more.
In an American perspective, Hitler was going to bring the war to the U.S. Also, a lot of factors could've resulted in Germany actually succeeding in winning World War II, Hitler was just stupid about it.
In terms of war, I think Hitler was close to being a military genius... but let's face it, the guy was the biggest hypocrite on the face of the planet. He hated jews... he was part Jewish. His version of the German master race was Aryan... let's face it folks, he wasn't blue eyed or had blonde hair.
If Japan hadn't made the mistake of attacking Pearl Harbor, we wouldn't have entered the war at that time. I'm pretty positive even if Pearl Harbor weren't attacked, America would've given up its neutrality and entered the war on the side of the allies. However, it would've given Hitler the upper hand in Europe if America had stayed out of the war longer than December.
Also, the fact that Hitler declared war on Russia... BAD move. This is what cost him the war, in my opinion. To quote Sum of All Fears "You don't fight America and Russia at the same time; you get America and Russia to fight each other." Two-front war basically killed Germany. If Germany hadn't attacked Russia, they could've focused ALL of there resources on the Western Front and not worry about Russian opposition. Let's face it, Hitler got over-confident.
Last fact, Atomic Bomb. Albert Einstein warned U.S. officials that Germany was building a very powerful weapon. President Roosevelt caught wind of this and decided to construct the Manhattan Project, etc etc. If Albert Einstein hadn't warned the U.S. about the possible building of the a-bomb by Germany... would Germany be reluctant when it came to using it? Safe to say we all know the answer to that one.
Instead of an alternate course in history, Hitler would've followed through with the Final Solution and proceeded on killing all the "inferior" races. America would not be as it is today, at all. The world would be German, because that's what Hitler was aiming for.
Do I think Germany could've won World War II? Absolutely. Hitler made very, VERY big mistakes, that if he avoided them, he could've easily defeated Britain someway, somehow. France was already wiped out. America wouldn't have entered the conflict if Japan hadn't intervened.
World would not be as it is today at all. It'd be a pretty scary place to be honest.