If were talking about Serena's serve peaking then 4-1 or 5-0 EASY. If her entire game is peaking including serve then 5-0 with graf lucky to win 5 games each match.
Really Steffi's backhand slice was potent weapon and peak Graf would have winning h2h vs all these players including Serena IMO.Graf's backhand would always be a liability with Peak Serena, heck peak Justine would have a winning record over Graf, as would peak Clijsters, peak Pierce, peak Azarenka, peak Kvitova.
Nope.Graf would win if both played their best.
Nope.Graf's backhand can handle anything Williams throws at it.
Perhaps.Graf is faster and has fewer lapses in concentration.
Nope.She can hold serve against Williams just as much as Williams can hold serve against her.
Nope.Graf plays the big points better.
Irrelevant.She is less likely to incur penalty points.
Nope.I'm not sure why Miami is on the list. Serena wins that one, Graf wins the rest.
The problem with that is Serena only switched to poly in 2009. So equipment is not a huge factor when it comes to peak Graf vs peak Serena. I think everywhere but clay it would be an uphill battle for Graf (unless the Wimbledon match was held on pre-2001 grass as the old grass would make her slice really tough to deal with). But I wouldn't count her out. Pre peak Serena lost to post peak Graf at Sydney but went on to beat her at Indian Wells. Graf didn't seem overly upset with the loss and seemed to already regard her as the heir apparent. It would have certainly been interesting to see how such a match up would have panned out over a longer period of time, over more matches.It's a flawed comparison because there's a huge difference between how tennis was played in 1988 vs 2002 and later on. The technological revolution with the poly strings was the huge game changer. Steffi would have been a different player if you put her in the 00's and so Serena wouldn't be the same player if you magically teleported her to the 80's.
If we had to go by just those matches as an indication, I would even slightly favour Graf in a hypothetical peak H2H. But the catch here is Serena's serve in 99 was still not nearly as potent as it would be and that's her biggest, most defining weapon. And Graf never faced a serve like Serena. So there's no way to evaluate this. It would appear that given other players' difficulties with Serena's serve, it's unlikely to be very much different for Graf. But we really don't know.Graf beat Serena twice in 1999 the only year they played, something that none of the players that would eventually have the most balanced h2h against Serena like Venus, Davenport, Hingis Capriati etc. could do that year. And even the only loss was a 3 long sets match.
Here are the records for 1999:
Serena vs Graf: 1-2
Serena vs Hingis: 3-1
Serena vs Davenport: 3-0
Serena vs Aranxa S.: 2-1
Serena vs Venus: 1-1
Serena vs Seles: 2-0
Serena vs Capriati: 1-0
Serena vs Clijsters: 1-0
Serena vs Mauresmo: 1-0
I think, if we assume similar starting conditions for both they would have a pretty leveled h2h but of course, it would all depend on many assumptions like injuries, technologies, adaptation, surfaces, experience etc. etc. It´s too subjective to compare competitors from different eras without extensive use of speculation