Ok the obvious three are Augustus, Trajan, and Hadrian. Solid emperoring all around there.
For number 4, I went with an odd ball choice of Diocletian. Not a nice guy by any means, but rebuilding a dying imperial administrative system counts for allot.
Constantine gets sentimental points, but when I took away religious favoritism, meh.
Marcus Aurelius gets my vote for most overrated emperor. His actual reign was mostly an endless military quagmire in the Marcomannic wars interspersed with plague. But he wrote some c level philosophy and gets used by classical historians as the last of the good emperors people act like he was Trajan.
I mean to Aurelius, neither of his crises was his fault and he generally dealt with both of them adequately. Maybe not one of the greatest, but he was a good one nonetheless.