No, the 90s and until they slowed the grass ought to be the weakest grass era. Why? Because at no other time in history has there been less rewards for good grass players. Before there were more important tournaments on grass, so more reason to be good at it. Now, the difference between grass and other surfaces is less, so being good on grass will also grant you success elsewhere.
seriously? if there was no reward for good grass players in 90s, how comes there were so many players with a game tailor made for grass, like ivanisevic, henman, philippoussis, rafter, krajicek, rusedski among others. if you say "no other time in history" that would imply this particular time in history is more rewarding for good grass players, yet there is not a single one grass specialist on top level.
in reality, sampras competed in much stronger competition and is, in my opinion, the best grass player ever.