Ancient Eastern kingdoms were headed by despots (i.e. one person held absolute power), while Greek and Phoenician poleis were either absolute democracies or absolute oligarchies - i.e. either the majority or the minority wielded virtually unlimited power. Moreover, they generally failed to create federations in the true sense of the word - their alliances were usually dominated by the hegemon city in a tyrannical way and were inherently unstable (the Athenian, Spartan and Carthaginian empires). Meanwhile, Hellenistic kingdoms were a mixture of despotism and poleis.
Rome was not a liberal constitutional republic (unlike the U.S.) - because liberalism did not exist yet and numerous atrocities were inevitable - but it was the highest political achievement up to that time. To a certain extent, it was the first government of laws, and not of men - the Aristotelian ideal brought to reality. It was a precursor to the republic of the Founding Fathers.
It is for this ideal of fundamental justice - not for persecution - that the early Christians hated Rome and considered it the new Babylon. The this-worldly success of the Roman way of life was a refutation of Christian other-wordly escapism - just like the success of America is a refutation of Islamist self-denial and self-flaggelation and is therefore hated by jihadists today.
Interesting insights on the nature of the Roman government can be found in the God of the Machine by Isabel Paterson.