Given the power vacuum that existed at the time, and how many of Hitler's own statesmen were bloodthirsty psychos themselves (seriously, look at some of the historical accounts of the S.S., even pushing past the bias some of those guys had issues), I somehow doubt the world would have been spared the hatred and destruction of WW2, with or without Hitler.
It's very easy to forget the conditions that allowed a political madman like Adolf Hitler to assume power in the first place. Germany wanted revenge for being handed the entire bill for WW1 (when a great deal of the blame also falls on France, Russia, and the now-defunct Habsburg Monarchy).
So no. Smothering baby Hitler to death with a pillow isn't going to accomplish anything apart from altering Godwin's Law slightly in the future.