In his conclusions about Antigonos the One-eyed, Richard Billows throws out some highly subjective, albeit reasoned claims. In some ways this is what the conclusion is for. Throughout the book he portrays Antigonos as the larger than life figure he was, as well as the general, diplomat and administrator that he probably was, but which we have no documentation for. In short, the claim is that Antigonos was the greatest of the successors because he was the lynch-pin that bound Argead Monarchy with the Hellenistic age, both as the epitome of a Hellenistic king and the progenitor of the institutions.
Antigonos was essential for the early Hellenistic period and implemented a fairly typical Hellenistic monarchy, not so much because he developed it, but because the Hellenistic monarchy was effectively the same as the Macedonian one and the most notable changes made were those of necessity, not design. As for his generalship, he was better than most, but Seleukos also has a claim to that standing since he was the architect of the Battle of Gaza in 312, defeated all attempts to remove him from Babylon and then commanded at Ipsos where he defeated Antigonos. If that is not a claim to being the superior general, I am not sure what is, but I digress.
As an aside in the conclusion, Billows mentions that the Seleukid Empire overextended into the east, separating it from the Mediterranean and allowing Asia Minor to splinter off. This, he claims, brought about its fall as it was unable to suitably respond to Rome and to the Parthians of Iran. He is both right and wrong. It is true that the Seleukid Empire over-extended, and fell to those two new powers almost two hundred years later, but neglects to mention that Seleukos founded his kingdom more than any other Hellenistic successor on the use of native troops, and his levy was from Babylon eastward. At Ipsos Seleukos led a varied force of heavy and light cavalry from Iran and Media, elephants from India, and infantry of a disparate background. Yes, over-extension became an issue, and yes, Seleukos was a Macedonian1, but his power base was the eastern satrapies. Later he and subsequent rulers attempted to reassert the empire as Mediterranean in nature, but it really was not. The struggle between that perception and the reality led to the over-extension, though it clearly did not result in immediate implosion.
1 Or an Epirote, if you believe Strabo about the ethnicity of Orestians, and Grainger about Seleukos’ family origin (citing the appearance of the name Antiochos attested only in that royal family). He probably was somehow related to the royal family of Orestis, though likely settled in northern Lower Macedonia during the time of Philip, so Seleukos would have grown up Lower Macedonian, but still had close ties westward.