First of all; it's very dilettantish to try describe way of history only from positions of guns, germs and steel. The same tried to do Marxists from economical positions.
The reason of Western success can't be just dumb luck, the advantages of domesticated plants and animals. We see, that all around the world any advantages and bonuses are complete useless if they aren't wisely managed. In the Japan there isn't huge natural resources, but Japan is one of the top world economies, the same situation in Singapore, but in Nigeria, country with rich oil resources, there are only middle-low success. Both of this nations had and still have access to Western technology and inventions, but why such gap?
In the end of movie Daimond declared, that it's very important to understand factors of guns, germs and steel, to UNDERSTAND. Maybe the main factor of world's difference is not geography, but people ability to understand and use things? The mental ability to understand. And in this case geography is only subordinated.