i think the list is solid, but on some of the shared years i think there are definite winners.
In 1952 I would eliminate segura because gonzales won wembley and had 5-2 edge on segura leaving a shared ranking for sedgman and gonzales
in 1958 i would choose sedgman because of 2 major wins wembley (the most important0 and aussie pro to gonzales one win at forest hills, and 4-2 head to head advntage for sedgman including both 5 set matches they played.
in 1959 i would choose be cause his overall win-loss percentage is better than hoad who had lot poor results in europe. gonzales won the us tour over haod. both players are otherwise egual with 5 event wins and one major each.
in 1972 i domn't see newcombe as a contender , the race is between nastase (winner of 12 events from over 30 starts and the biggest event forest hills) against smith (9 wins from 21 starts, wimbledon and the davis cup) with vote going smith because of his 4-1 edge over nastase.
in 1975 everybody but the atp choose ashe. ashe won 9 events including wimbledon and wct finals and won his only match against connors, who was ru at wimbledon and forset hills and won 9 minor events.
in 1976 connors deserves because he won 12 events to borg's 6 and had a 3-0 head to head over borg.
in 1977 i agree its betwee borg and vilas. I would choose vilas because he won 2majors and was runner up in the aussie to borg's one major. outside the majors vilas won 16 events to borg's 10. borg's 3-0 head to head is his only claim and is not sufficient on its own.
in 1978 i would choose borg with 2 majors to connor's 1 and 3-2 head to head advantage.
in 1989 i would choose becker with 2 majors to one for lendl, and becker's big davis cup win and his 2-0 head to head edge on lendl. lendl 's only claim are 10 event wins to becker's 6