Both Mesopotamian and Egyptian civilizations emerged around major river systems. These civilizaitons began in these areas because the flooding of the rivers created fertile soil and allowed people to succeed in agriculture, which was a major factor in the emergence of civilizations.
While both civilizations centered around their major rivers, there were some differences in the impact of the rivers. For example, the flooding of the Nile in Egypt was much more reliable and "on time" than that of the Euphrates and the Tigris in Mesopotamia. The people of ancient Egypt were able to develop a calendar around the flooding of the Nile. It's flooding was more dependable than that of the Tigris and Euphrates.
Egypt's natural surroundings were also much more conducive to the development of a civilization. The Egyptian civilization was surrounded by deserts on both sides. These deserts, along with the rough sections of rapids on the Nile River upstream from the main center of civilizaiton, provided an isolation for the Egyptian society that the Mesopotamians didn't possess. The region of Mesopotamia had less natural barriers that left them much more open to invansion from outsiders.