Yes, that is what I would look at to determine someone's peak. Here's the 16 most dominant performances (top 3) by games won % against the top 10.
1 | David Goffin | Tomas Berdych | 09-05-2016 | Rome Masters | Clay | R16 | 6-0 6-0 | 100.00% |
1 | Roger Federer | Gaston Gaudio | 14-11-2005 | Masters Cup | Carpet | SF | 6-0 6-0 | 100.00% |
3 | David Ferrer | Gaston Gaudio | 02-05-2005 | Rome Masters | Clay | R16 | 6-0 6-1 | 92.30% |
3 | Joao Sousa | David Goffin | 19-03-2018 | Miami Masters | Hard | R64 | 6-0 6-1 | 92.30% |
3 | Jonas Bjorkman | Mariano Puerta | 26-09-2005 | Ho Chi Minh City | Carpet | SF | 6-1 6-0 | 92.30% |
3 | Kevin Anderson | Kei Nishikori | 12-11-2018 | Tour Finals | Hard (i) | RR | 6-0 6-1 | 92.30% |
3 | Michael Chang | Alberto Berasategui | 15-11-1994 | Tour Finals | Carpet | RR | 6-1 6-0 | 92.30% |
3 | Mikhail Youzhny | Rafael Nadal | 31-12-2007 | Chennai | Hard | F | 6-0 6-1 | 92.30% |
3 | Novak Djokovic | David Nalbandian | 09-06-2008 | Queen's Club | Grass | SF | 6-1 6-0 | 92.30% |
3 | Novak Djokovic | Dominic Thiem | 15-05-2017 | Rome Masters | Clay | SF | 6-1 6-0 | 92.30% |
3 | Philipp Kohlschreiber | David Ferrer | 18-05-2008 | Dusseldorf | Clay | RR | 6-1 6-0 | 92.30% |
3 | Robby Ginepri | Marat Safin | 10-03-2003 | Indian Wells Masters | Hard | R16 | 6-0 6-1 | 92.30% |
3 | Robin Soderling | Tomas Berdych | 11-07-2011 | Bastad | Clay | SF | 6-1 6-0 | 92.30% |
3 | Roger Federer | Andy Murray | 09-11-2014 | Tour Finals | Hard (i) | RR | 6-0 6-1 | 92.30% |
3 | Slava Dosedel | Jonas Bjorkman | 20-04-1998 | Monte Carlo Masters | Clay | R32 | 6-1 6-0 | 92.30% |
3 | Tommy Haas | Alex Corretja | 09-10-2000 | Vienna | Hard (i) | R32 | 6-1 6-0 | 92.30% |
As we can all see Goffin (Co-Goat), Sousa, Kohlschreiber, Ginepri, Dosedel have a higher peak than Sampras whose best is 80% (i.e only 60th rank). Also Thiem's best is ranked 313, while Philippoussis' is 60 and Baghdatis' is 146.
Source -
https://www.ultimatetennisstatistics.com/topMatchStats. Sort by games won% and filter by opponent - vs. top 10. It doesn't display matches before 1991 because points stats aren't available for those matches. So I went and looked at Pete's match results vs. top 10 before then, and he didn't do better than 80%.