After a succession of civilizations ruled over mesopotamia, which group was the most enduring and ultimate victor?

The answer would be the Persians. Mesopotamia was under the control of the Parthian Empire. Mesopotamia turned into a battleground between the Romans and Parthians, with western parts of Mesopotamia going under vaporous Roman control. In AD 226, the eastern districts of Mesopotamia tumbled to the Sassanid Persians. The division of Mesopotamia between Roman (Byzantine from AD 395) and Sassanid Empires endured until the seventh century Muslim victory of Persia of the Sasanian Empire and Muslim triumph of the Levant from Byzantines. Various basically neo-Assyrian and Christian local Mesopotamian states existed between the first century BC and third century AD, including Adiabene, Osroene, and Hatra.

In the midwest because it has more moderate climate than the north or south west which makes farming far easier.