At best she could be considered one of the best women players, not the best overall "player", meaning both sexes.
While Serena has more GS than Graf (by one), it is Graf that has many other coveted records and better overall career stats. As far as making the comedic leap that Serena is the best player, not the best "woman" player:
See stats again. If you are basing it on # of Grand Slams, Novak Djokovic has 24, Serena has 23. How convenient it is to believe Serena should be compared with the men without matching Novak's number of GSs or ever once having to play a man to prove it.
