Re: Peak Serena vs peak Seles
Here are how some of their stats compare peak to peak:
Serena in 2002-2003: Won 5 of 6 slams played (83%), won 2 of 3 WTA Championships/Miami/Olympics (67%), 56-5 in 2002 (91%), 8 of 13 tournaments played won in 2002 (61%), 2003 singles record 38-3 (92%), won 4 of 7 tournaments played (57%)
Seles in 2002-2003: Won 6 of 8 slams (75%), won 3 of 4 WTA Championships/Miami/Olympics (75%), 74-6 in 1991 (92%), 10 of 16 tournaments played won (62%), won 10 of 15 tournaments played (67%)
So very close stats all around. The biggest difference is Seles's winning 67% of tournaments played in 1992 vs 57% for Serena in 2003, but the clay season had just finished so Serena's percentage was likely shooting way up had she been able to complete the year. That and Serena winning 83% of the slams she played in 2002-2003 vs Seles winning 6 of 8 slams (missing Wimbledon is basically a write off as she was never winning it anyway) for 75%.
Overall I would still give the edge to Serena since she had tougher competition, faced a stronger and deeper field. Also since she could win on all surfaces, unlike Seles. She also owned her biggest rivals moreso than Seles, the only top player or any player for that matter to beat Serena more than once was Henin on clay 3 times, and Henin could not come close to Serena on any other surface then. Seles meanwhile lost 3 times to Graf (3 out of 4 matches), 4 times to Navratilova, 2 times to Capriati, 2 times to Sabatini, and once to Sanchez Vicario. Lastly I am completely sure had Serena been able to play the 2002 Australian, 2003 U.S Open, and 2004 Australian Open she wins all 3 and wins 8 of 9 slams, which is greater than Seles's peak streak of 7 of 9.