Boardman was quite good.
Claytor was excellent except he left a mess for his successor. I can't make any other crititcism; he preserved and enhanced Amtrak during a period when passenger rail was actually declining in popularity. Most of the other Amtrak CEOs actually had the "wind at their backs", with constant rising passenger demand.
Reistrup and Gunn were both very good at running a railroad but not politically savvy.
So that's the four really good Amtrak CEOs.
Downs was the absolute worst by a country mile, probably followed by Anderson. Downs screwed up things which shouldn't be possible to screw up. So did Anderson, but Downs made a bigger mess. Downs also screwed up multiple other transit agencies in ways which shouldn't have been possible.
Boyd was also bad.
Warrington tried, while dealing with an impossible political situation, and the things he tried weren't actually disasters, though they weren't successes either, so I put him in the mixed category.
Hughes, Kummant, and Crosbie made no impression and frankly neither did Moorman. Flynn also hasn't yet.
Lewis is another mixed bag: most of his work was good, but he made probably the single biggest error in the history of Amtrak -- telling Congress that if they gave him several billion dollars he wouldn't know what to do with it.