Geographic factors affect the development of a specific region or nation in a couple of ways: 1) Climate affects how habitable a region is, and as a result, very few nations may survive in harsh climates and few may thrive in less-than-ideal climatic conditions. If you notice, the power in the world lies in the Norther Hemisphere. This is not a coincidence, but a result of the poor land fertility, high water scarcity and high disease outspread in tropic areas present in more abundance in the Southern Hemisphere. People in those regions have had to work twice as hard just to survive and have had fewer development opportunities than northern countries.
2) Natural resources available in the region also play a big role in how much a region or country develops. While not a permanent factor, as most natural resources eventually become depleted, it does offer an advantage or a boost to a country in a resource-rich region.
3) Location, in terms of access to water, has played and will probably continue to play a big role in how developed a country becomes. Having access to waterways is important for trading, as many nations in the world continue to use ports as a "trading grounds", allowing for profits and prosperity. Additionally, landlocked countries have added expenses in terms of land-transportation and lack of defense on water ways.
4) Environmental stability plays an unpredictable role as well. If a nation is located within a radius of known environmental danger, such as tornadoes, earthquakes, tsunamis, etc. it must work to protect itself against them, thus lowering its chances of progress.
If you observe the world and its countries in terms of these geographic factors and the compounded effect of more than one of the above factors acting together, it's easy to see how and why some countries have prospered and others have not.