The story goes, Atari planned on releasing certain games for the 5200, but not the 2600, to encourage more sales of the newer console. Then, when it became apparent the 5200 was not going to eclipse the 2600 in sales or popularity, several of those games were developed and released for the 2600 after all. This explains why 2600 Galaxian came out a year after 5200 Galaxian, when most common games were either released at the same time or saw action on the 2600 first.
Whatever the reason for the 2600 version's lax timing, coming out four years after the arcade game, this is a solid port. There is a distracting orange border around the playfield, the aliens are fewer in number and have different shapes than their arcade siblings (perhaps a nod to 2600 Space Invaders doing the same thing?), and the enemy attacks are a little more predictable. Still, Atari's cartridge provides a perfectly serviceable game of Galaxian, better even than the Commodore 64's offering. It may not look or sound the greatest, but it does just fine.
Grade: B.