Greatest Roman Emperors

I'm really confused, because I wrote an extensive explanation for why I think Trajan is the greatest Emperor and it is no longer here. I will come back and rewrite everything. I think.

There seem to be two main knocks against Marcus Aurelius: The first and most oft referred to is his appointment of Commodus as successor. And the second is that his reign was marked with turmoil as plague devastated the Roman population and as Rome faced the constant threat of invasion from the Germans to the north and the Parthians to the east. To the first of these, I would simply point out that even the strongest of men would be more inclined to commit their legacy to their children rather than to some capable and trustworthy fellow that bears no relation. Everyone wants the best for his children, and everyone is more inclined to believe and hope the best for them, even when everything tells you otherwise. Furthermore, had Marcus not appointed his son heir, when he did die, his successor would undoubtedly have killed Commodus as rival claimant to the throne. One cannot expect Marcus, no matter how great a man he might have been, to endure that. To the second criticism, I would say that, rather than diminishing his value, the circumstances of the empire during his rule, only increase his greatness. The empire flourished under Trajan, yes. And, undoubtedly, much of that flourish is due to the greatness of that emperor, but true greatness is best seen by contrast, and the mettle of a man is demonstrated through testing, and the fact is that Marcus Aurelius did more for the empire under worse conditions than any other man who ever lived. In addition to all of this, Marcus was truly a great man. He seemed to genuinely rule for the benefit of the governed and not for his own sake. In saying this, I am not under some delusion that he displayed no self interest, nor am I under the impression that he wasn't, to some degree, arrogant. He was not a perfect man. But nobody is, right? And, I do have to say, that of all the truly great world rulers that I have ever encountered through study, I have never seen one so selfless and moral as Marcus Aurelius.