Galileo never quite got the accuracy of 9.8. Here is a summary from another website:
The first systematic tests of the universality of free fall were done by Galileo [2], who measured the acceleration of freely falling objects, or of objects rolling down an inclined plane. Such an approach suffers from great inaccuracies, which are related to the short time scales involved. Indeed, Galileo was unable to accurately determine g, the gravitational acceleration at the surface of the Earth, due to the lack of an accurate clock. Galileo concluded that a much better way to check the universality of free fall was to use a pendulum. Newton, and following him others, improved on Galileo’s experiments, and were able to determineg quite accurately.