Godzilla’s worldwide popularity has spawned the atomic beast’s portrayal in several classic commercials, most of which didn’t have a true storyline attributed to it, but merely featured the kaiju’s image. For those who wish to see a listing of almost every G-commercial that has ever been produced up to the late 1990's, acquire a copy of Ed Godziszewski’s excellent book, THE ILLUSTRATED ENCYCLOPEDIA OF GODZILLA (this book is now hard to acquire, since it was only offered via mail to readers of G-FAN magazine, only about 2000 copies were produced, and Toho eventually took notice and asked that Daikaiju Enterprises no longer offer the book).
However, G-FAN editor J.D. Lees has recently completed a new tome, THE OFFICIAL GODZILLA COMPENDIUM (which was officially authorized by Toho).

The number of these commercials, both in and out of Japan, are much too numerous to include here. Rather, the focus of this section will be on the two most classic and well-known commercials ever made, both of which contained truly outré storylines, but neither of which was serious in tone, and would likely be of the most interest to G-fans. The second of the two commercials was surprisingly respectful, but the original was not.
In fact, most commercials that appeared in the U.S. featuring Godzilla’s image were downright impudent, including one in which Godzilla was mentioned, but a stock footage clip of Gamera was shown instead! It’s quite hard to believe that whichever company produced this atrocity actually believed that no one would notice.

The following two links will deal with the two most memorable Godzilla commercials to ever hit the small screen in the U.S.

Dr. Pepper's 'Out of the Ordinary' Godzilla commercials (1985)
Godzilla vs. Charles Barkley (1992)