That's quite silly. The Meditations are a very mediocre book, there's nothing visionary in it. A really great/good emperor would have written a political manifesto instead of a boring book about philosophy!
Nope. Nerva was a quite influential emperor, as he founded the alimenta system (although only on a private base, it was Trajan who founded the public alimenta). In some way, the alimenta system was the embryo of a welfare state Rome wanted to be, but Rome never became (Rome couldn't become such a social state given its low technologic and industrial level).
So if you conquer a territory and your successor gives it up, it's your fault that you conquered it in the first place? Trajan receives a lot of criticism because he invested a lot in the Parthian campaign, but the profit of Rome controlling Mesopotamia and the trade with India would be huge. In fact, Rome conquering Mesopotamia would butterfly away the two-front war against both Germania and the Sassanian Empire.
Trajan is still the best Roman Emperor, the greatest in many aspects - even better than the founder of the empire, Augustus, who spilled much blood to come to the throne, including such great men like Cicero, Cleopatra, Cassius or Brutus.
Trajan was a wise and benevolent emperor, the best example for a working monarchy/dictatorship.
Well, Lusius Quietus had crushed the most important Jewish revolts in 117 CE, and the empire was ready to launch a second great offensive against Mesopotamia. With some heroic efforts of a great emperor (like Trajan or Quietus), Rome could then have retained Mesopotamia. Hadrian might have been clever, but he didn't realize the potential of the province of Mesopotamia.
It's not even clear that Trajan wanted Hadrian to become his successor, maybe Trajan changed his mind just before his death, but it was too late then and Trajan's wife made up Hadrian's adoption. Furthermore, he was a quite cruel leader who had the members of the senatorial opposition (people like Quietus who wanted to continue the war against Parthian) murdered (without a due process?).
But on the other hand, Hadrian really cared for the empire, so from a certain point of view, we can consider him as one of the "good" emperors.
However, never forget the mistake of surrendering the strategic initiative to Germania and Parthia!!!
Also, he (re)introduced these ugly beards - poor Antinous...
I agree with you, Antoninus Pius was an idiot.
Well, I already said why I don't like Aurelius - he should have written a more interesting book (like Prophyrogennetos who wrote a book about politics).
But in fact, Aurelius only had to pay for the mistakes of his two predecessors. Antoninus had allowed the Germanic tribes to rise (for example the Marcomanni), whereas Hadrian had withdrawn from Mesopotamia. Now Aurelius had to fight on both fronts, against Germanic invasions and against invasions from Mesopotamia.
As to Commodus, it was the logical choice. Trajan and Hadrian were interested in men, so they couldn't father a son. Marcus Aurelius had a son, and if he hadn't appointed him successor, a civil war could have been triggered even earlier than OTL. Never forget that the "five good emperors" were an "adoptive dynasty" by force and not by choice.
And where,
@HIM Dogson, is Lucius Verus?