There is a metric for judging college football coach performance called Program Impact or something. It throws out a coach's first two years and adds the results for the first two years they are gone. It is designed to not hammer coaches for inheriting a train wreck and give them credit for the state of the program when they leave it. It recognizes the importance of Jimmies and Joes to team performance.
I looked at this for Georgia Tech, starting with Bobby Ross.
First the actual records, per Wiki.
Ross 31-26 54.4%
BL 11-22 33.3%
O'Leary 53-30 63.9%
Chan 44-33 57.1%
PJ 83-60 58.0%
Geoff 6-16 27%
Ross is clearly underrated for the job he did here, when you only look at W-L. BL clearly sucked, as he did IRL. George was good. Chan and Paul show as so-so but winners. Geoff shows worse than BL, which is nonsense.
Now for the Program Impact records.
Ross 36-21 63.2%
BL 12-21 36.4%
O'Leary 56-31 64.4%
Chan 50-28 64.1%
PJ 69-69 50.0%
Geoff 0-0 N/A
This shows Ross doing a great job, which he did, and George doing a slightly better job, which given the total body of work is not unreasonable. BL is still BL. Chan gets a boost from the outstanding young talent he left in the program. Paul gets a double whammy from inheriting outstanding young talent and leaving the cupboard bare of experienced talent when he left, which if you look at the attrition and poor performance of so many of the 2016 recruiting class in particular but other classes as well, is justified.
And it gives Geoff a clean slate, with accountability next year. Anyone who is fair would agree to that.