Uh, no one is expecting her to have the same results...it has been 18 years since 1995...she is over 40...for her to have the same results would be miraculous. The point is if the game was "so deep" as you claim, then a player who was lower end top 10 in her prime shouldn't be top 50 when over 40 years of age.
You get the point of my post. I think Kimko's results in late years show how good a player she is and how a top player can adapt and play in a different era. Of course, you can't expect her to be top five by now, because she is a top 40 player aged over 40! I don't think you can compare her to Navratilova for 3 reasons: Martina retired still a top ten but not top five at just 38 years old, and Kimiko got back to the tour at that age, and is now 43 (five years are to be considered after a certain age
) just to try to play again at that level, and that leads to my second reason, Date had to re enter a Tour she had left more than a decade before, and everyone knows how hard is for a player after a long (more than 6 months) absence to get a rythm again; while Martina never stopped until 1994, she was playing all those years and living the daily evolution of the game and keeping match play and competitiveness intact. And the biggest reason is that Martina could compete at a higher level near 40 not because the tour was weaker, but because she had been the one who had pushed the limit, the player who took the game and power to another level and made everyone work to keep her pace, she reigned supreme for several years and had an unmatched Golden Run when she was several steps ahead of the rest of the Tour, so of course she could be competitive with most players in her late tennis years because she had made the game evolve. Kimiko was a top ten player in her peak (not consistent top five to be so considered like, for instance, Martínez), so she was following a tide in tennis, not swimming ahead, for her to be still among the top more than a decade later. It's remarkable enough that she can still compete, and earn the occassional upset that, if you believe the current game apostles, players from the past would never be able to, as though tennis was played with wooden rackets back then!
I can see the general speed and power of the game has increased, but most of the top players are not to be feared compared to notable players from the past like Navratilova, Sabatini or Seles, I really don't see how they could not compete and beat today's players provided the rackets and, of course, if they could be in a comparable age. Serena at a her peak level is another thing, the same as I don't see Zvonareva, Kvitova, Radwanska or Wozniacki having much to do against an A-game Graf or Seles; Azarenka and Sharapova could her her own a little more but they are an echelon below to the German and the now American: the very best players of different eras are better comparable among themselves.