The first portable installment in the Galaxian series, players control a lone starfighter in its mission to eradicate the hostile Galaga forces before they take over Earth.

[1] In each level, the objective is to destroy all of the Galaga aliens, which fly into formation from the top and sides of the screen.

[1] As in other Galaxian games, enemies will divebomb towards the player and attempt to collide with their ship while also firing projectiles.

Minor assistance was provided by Now Production, a Japanese developer that collaborated before with Namco on a number of arcade conversions.

[3] As the first portable installment in the Galaxian series, '91 is based on the arcade game Galaga '88 (1987) and its TurboGrafx-16 home conversion (1989).

[8] The graphics, in particular, were well-liked;[2][12] Demoly enjoyed its sprite animations and a reviewer from Mean Machines Sega felt it was one of the game's strong points.

[8][14] Critics liked the gameplay itself for being fun and well-designed,[8][12] with the Mean Machines reviewer calling it "a good blaster" for the Game Gear library.

writer felt that the limited screen size made it harder to avoid enemy shots and the graphics look squashed.

[15] In a retrospective on the franchise in 2006, Stuart Campbell of Retro Gamer showed his appreciation towards Galaga '91 for being built around the Game Gear's hardware and battery life.