Haruo Nakajima, for those that don't know, was the man in the Godzilla suit from the beginning. Sure, there were a few other actors that helped out here and there, but he lasted until 1972's GODZILLA vs GIGAN (which is enough to do anyone in, believe me). He was also many other monsters and has said his favorite role was that of Gaira from WAR OF THE GARGANTUAS in 1966.
I met the man once, way back in 2000 at that final G-Fest in Hollywood, and he was great. I hope he has many more happy birthdays to come! This is a short video of his last time in a Godzilla suit, which happened in 1983.