A single screen and lots of enemies to shoot defines this genre.
Gun Fight
Arcade
1975
Boot Hill
1977
Space Invaders
July 1978
Galaxian
October 1979
Radar Scope
December 1979
Ozma Wars
Space Beam
1979
Astro Fighter
Attack Force
Stratovox
1980
Atari 2600
Phoenix
Moon Cresta
Carnival
UniWar S
Galaga
1981
Centipede
Gorf
Demon Attack
1982
Millipede
Gridrunner
Commodore VIC-20
Satan's Hollow
Pleiads
Pisces
Exerion
1983
Abductor
Arcadians
BBC Micro
1984
Gaplus
NES
Sega-Galaga
Sega SG-1000
Return of the Invaders
1985
Battlantis
1987
Galaga: Demons of Death
1988
Galaga '88
PC Engine
1989
Pang
Amiga
1990
Space Invaders: Fukkatsu no Hi
Game Boy
Space Invaders '91
SEGA Genesis
Deluxe Galaga
1995
PlayStation
1999
Space Invaders Extreme
PSP
2008
Galaga Legions DX
Xbox 360
2011
Verminest
Windows
2012
Titan Attacks!
PlayStation 4
2014
2016 (orig. 1979)
Centipede: Recharged
PlayStation 5
2021