Re: Napoleon
I think a what if scenario would have been, what if Napoleon hadn't had his insane need to invade England, and had instead tried to make the Treaty of Amiens work. Without a hostile Great Britain to cause headaches and finance continental enemies, he might have gotten a lot further in his dreams of continental domination.
In real history, of course, he had to have it all, including England, but with a little more moderation France could have been the greatest nation in, and de facto master of, continental europe, for a very long time. She would never have collapsed into the second rate Great Power she became. You have a vastly different future right there, with perhaps french being the most influential language on the planet, Germany never unifying etc.
Re: WWII
If the Nazi's hadn't done their little number on Russia, well, some claim Russia had invasion plans all of its own for the 1941/42 timeframe. The Russians had around 35.000 tanks v.s the German 6.000 at the onset of the war in the Eastfront. I don't remember the exact numbers but it's in this ball park. The russians had an amazingly advanced offensive army for that time, at least as far as tanks/paratroopers/number of air assets goes. Now Stalin does a little blitzkrieging of his own, capturing the critical to the Nazis Ploiesti oilfields. High russian morale. No implosion of the russian army. The Nazi warmachine without oil. He catches both the western capitalist pigs and the nazis with their pants down, at their weakest, completely unexpected and the western nations thouroughly demoralized.
It's a little known fact that Stalin ramped up Soviet military production to wartime mode at the onset of WWII, fully expecting to take advantage of any opportunities offered. How do the dice fall next?