Godzilla remains one of my favorits NES games, and with many good reasons.
The music was really weird, but I didn't expect a Neptune or Mars soundtrack to be jammin'. The sound effects were right on, so no complaints there. I particularly liked the punching and flame breath sounds.
The premise is simple: smash it all! Godzilla is travelling throughout the solar system, landing somehow on every planet (when you are controlling a gigantic beast of legend, you'd better be able to suspend reality), clearing it of hostiles, taking out a boss, and doing it all over again. I seem to remember Mars being very unpleasant. The path chosen to get to the boss is not totally linear, but the choices are limited. Speaking of bosses...
All the classic foes from the Japanese movies, such as Gigan, Mecha-Godzilla, Hedora, and King Ghidora. These clashes are strictly boss fights and present the greatest challenge to completion. To confront them, you have to get through long levels replete with turrets, weird vicious biologics, as well as air and ground based assualts. Luckily, you're Godzilla, so most of this stuff can be survived. To fend for yourself, you can punch, kick, and smack with the tail. When in a jam, blast them with the energy breath. That's particularly gratifying, since it clears a path rather well. Combining these assauts (and knowing when to jump and duck) are essential to defeating the bosses.