The early 1990s was not a good time to be a bad guy. Every time your gang of thugs, band of ninjas, or evil dictatorship tried to take over the Earth you could pretty much count on a trio of heroes to come walking left to right and single handedly destroy your entire army.
In this particular case the bad guys are aliens, and the good guys are the "Alien Busters," a special team of three people (named Karen, Garth, and the robot Scooter.) The game plays like an alien invasion version of Golden Axe, down to the standard short combo and large screen clearing super attack. This particular time around there isn't as much of a "wow" factor involved (Karen's large nuclear missile is effective, but not as visually impressive as a giant Dragon breathing fire on everyone.) There also isn't really much of a difference between the three characters as far as abilities - I'm sure one of them is stronger and another is faster, but you wouldn't know that from actually playing the game or anything.
The majority of the game is made up of the generic side scrolling beat'em-up portions, which play as decently as any other game from this era. The Aliens try to surround you, and all you need do is keep them all one one side, repeatedly torching, body slamming, and jump kicking your way through them all. The Aliens have a tendency to "hide" inside of objects on the screen, however once you see this happen you can pretty much assume that every object you see will have an alien inside it (and you'd be right.)
Inbetween these segments are short pseudo first person shooter segments. These tend to play less like a FPS as we're used to today and more like the bonus levels from Shinobi. You fire your Ghostbusters-like ray at various aliens that appear on the screen, blow up shelves, display cases, and other objects to get powerups, repeat. Also occasionally there are short "running" sequences, where for some reason your character is running all fast (which looks pretty stupid, it would have come off much better if you were in a car or something.) Here the gameplay changes to a side scrolling shooter style. These portions provide a needed break between the beat'em up segments, but are too short and way too easy.
The aliens themselves are the highpoint of the game, each being some kind of hideous blob-like Lovecraftian mess of teeth, tentacles and eyeballs. Bosses have an impressive design, but lack a certain "oomph" that other games of this type have. For instance, they are "gimmick free"- part of the appeal of these games is that boss characters each have a unique way of attacking that requires more than the usual walk-up-and-kill-it approach. Here the bosses just have a tendency to bump into you.
This is the feeling one gets from the whole game, that of wasted opportunity. The gameplay is pretty generic for a game like this. At no time does the action really heat up, and before long you're robotically going through the paces.
Graphics: Small characters make up for their lack of colors with a good amount of detail. The main characters seem to be rather jerkily animated, as in there seems to be missing frames or whatnot. The design of the various aliens look good, too bad all they really do is walk around and bump into you.
Sound: Zaps and bangs, and a weird alien squeal whenever something dies. Just like in Golden Axe it seems the music has to stop whenever we hear one of these digitized effects, however this time around it's not as jarring.
Gameplay: Things start off good but quickly degenerate into alien monotony. The shooting and running sequences attempt to break the game up and keep the pace going but are too underdeveloped, and almost seem to be an afterthought.