You can always compare. I don't know what the criteria is for "good translation."
The City of God against the Pagans. Translation by R. W. Dyson. New York : Cambridge University Press, 1998. ISBN 0-521-46475-7
The City of God. Translation by Henry Bettenson. Harmondsworth, England: Penguin Books, 1972.
The City of God. Translation by Gerald G. Walsh, S. J., et al. Introduction by Étienne Gilson. New York: Doubleday, Image Books, 1958.
The City of God. Translation by Marcus Dods. Introduction by Thomas Merton. New York: The Modern Library, a division of Random House, Inc., 1950.
The City of God. Translation by John Healey. Introduction by Ernest Barker. New York: E. P. Dutton & Co., 1945.