In the original Godzilla, it is all but directly stated that he was at the center of a thermonuclear explosion and survived, and that nothing that is not stronger than an H-bomb can harm him (when Dr. Yamane said “Godzilla was baptized in the fire of the H-bomb. What could kill it now?”). If that's not good enough, watch this documentary at 3:20. Akira Ifukube says (referring to WWII) "In the end the Japanese had fought with all their spirit, but it was modern technology [the atomic bomb] that defeated them.", and then "Godzilla is undefeated by modern technology.", and finally, if even that is not stating it directly enough, "He is stronger than the weapons that brought Japan to it's knees."
I know stating any of this may seem unnecessary now that the G2014 trailer has shown him surviving being nuked, but I just wanted put this out there in case a certain someone who used to write many multi-page rants on this site (you know who I'm talking about) tried to argue, "Well classic Godzilla still would totes be killed by nukes."
