I agree - but I also think that one of Rome's greatest and most unique strengths was its liberal attitude towards citizenship. It seems so obvious to us now, but if you can put yourself into the mindset of someone from the 3rd BCE, it is a revolutionary idea that someone can become a citizen of a state other than that of their birthplace: this almost never happened in the Golden Age of Greece, for example (even the son of Pericles by Aspasia was not an Athenian until the law was amended). For another, there's Carthage: before the Punic Wars, Carthage's ager publicus was much larger and richer than Rome's, not to mention the huge fleet of warships and merchant vessels. But no matter how hard the Libyo-Phoenicians, Numidians, or Iberians fought for Carthage, the franchise never expanded, and thus there were never as many people with a deep vested interest in the state as there were for Rome.