Being that we are talking about martial arts, maybe they judge that on how well someone can control them or kick their asses in the most efficient ways.
Excuse me for saying this [I know you are being facetious in your comments herein]if kicking someones butt is the yardstick of a great martial artist you are sadly mistaken.I have known Glaswegian dwarves , who when involved in a rammy[fight ] could administer the world renowned Glesca Kiss[ a seriously dangerous head butt].These diminutive hard men did not study I/P/ Chinese Martial Arts or even Aikido.They had bottle[usually a beer bottle -empty of course -joking here] Bottle /courage is needed not fancy Hakamas and twirly ribbons.]
My own judo teacher was 90% disabled.He hobbled along the street.On the tatami , nobody ever threw him in all the years I knew him.He was to us [his students]immovable.
For me a good Martial artist is a person who knows his/her trade , shows compassion and understanding to others and conducts him/herself in a correct manner both on and off the tatami.
If beating someone up is a measure of a martial artist why spend years training in a Do, just carry a big baseball bat or an Uzi? Cheers, Joe