I guess you have to start by defining what you think athletic ability is.
I think of it in terms of raw speed, agility, jumping ability, hand to eye coordination, footwork.
PG
Flynn is the gold standard here. Really fast, could jump really well, could whip a pass down the court with little effort, super agile. Pearl was a good not great athlete IMHO. Not much of a jumper. Not super fast. Sherm was fast and could jump and probably is my second team guy. Though Eddie Moss should be considered as well. He was really fast, strong, agile and was a terrific leaper. Our best man defender at guard in the JB era.
SG
I didn't see Bing play at Syracuse. Too young. I did see him play in the NBA in the second half of his career and even then he was a freak athlete. Really fast, great leaper, agile and so smooth. I give him the nod over Stevie by a hair. Tony was a great leaper but not as agile or quick as the other guys.
SF
David Johnson was a fantastic athlete. Seemed to do something remarkable every game he played. Fast, strong, so coordinated, so great in the air.
Wes wasn't as strong but was maybe a hair faster and maybe a hair more agile. Jerami did everything well and was the best athlete on the court just about every time he played at SU but I can't give it to him. He was too reserved and perhaps didn't show everything he was capable of all the time when he was here. Paul was strong and was a very good leaper and had good speed but not like DJ and WJ. I give this to David by the smallest of margins.
PF
I have Billy Owens, Hakim Warrick, Carmelo Anthony and Derrick Coleman as my finalists here. I think those are the finalists. Pretty good group
Billy wasn't a freak athlete. He was a really good athlete who was also really smart. Hak had great leaping ability and body control and I think has the best catalog of blocks thrown down at Syracuse in history. Really good rebounder and shot blocker for a forward. But maybe not as well rounded as some of the others here. Melo had the best first step of any player I have seen play at Syracuse. Also exceptionally smart but not a crazy good leaper, not super fast. He beat you more with his mind than his body. Derrick was a very good leaper and had that quick jump to beat others for putbacks. Also was really good bringing the ball up (Owens and Melo were no slouches here either) and was a terrific passer for a forward. Best outlet passer I have ever seen at the college level (did not see Unseld at UL). Gotta go with Derrick here. Honorable mention to Leo Rautins, who did everything well and if he was 100% might have challenged Derrick.
C
Rosie was really agile, really quick, could jump really well and had a lot going on. Maybe a bit underappreciated because he played so long ago and did not play afterwards in the NBA. Rony was as fast as anyone who played center at Syracuse. Another really good leaper. BMK might have been even more agile but that was his only great strength and he didn't do much of anything else really well. Conrad was also very fast and could jump out of the gym. Yes he was wild and out of control a lot but he was really fun to watch running around like a madman. Etan and Mookie were fine athletes too. Really close here but I think I have to go with Rony. At his best, he dominated more than the other guys.