If Zombie Nation was released at any other time it would be a completely unremarkable horizontal shmup. It doesn't control that well and is fairly boring.

However, it's due to the fact that it's an NES game it attracts attention. Sure, SEGA and many later consoles had more horror-themed games, but for NES it was pretty rare, and to see a game where you play as a decapitated head shooting buildings and eating people was a hell of a surprise.

Zombie Nation is quite bad and pretty much worth playing only for its presentation. In fact, first level is probably the best one, as you spit bullets all over a giant city decimating buildings and making people fall off roofs only to consume them for power-ups. Later levels become more and more abstract and feel way less interesting due to that.

The game doesn't have much in terms of power-ups, just a linear progression. Its movement also kinda sucks with your character being able to slide across predetermined rows as opposed to having full movement. Like, if you just lightly tap down, your Head won't go down for a pixel, but rather a full row.

If this were a game about a helicopter, it would be forgotten entirely. It would be one of those games that I'd play and as time comes to write about it I'd need to look at my history to see its name. It lives and dies on its concept, but thankfully the concept is very fun and playful. I'd recommend a playthrough.