Atari 2600
Developed by Atari in 1980. The very first official commercial port of one company's game to another company's console. As the first conversion, the emphasis was not on capturing the original look of the arcade, but simply the game play. To that end, Atari did a good job, and the game proceeded to sell the system to homes that didn't yet possess one just so people could play Space Invaders at home. Multiple variations of game plays exist, including different ways for two players to play cooperatively or competitively. A cheat enables one player to fire two bullets at once, instead of just one, by holding the reset button down while powering the system on.
Atari 5200
Developed by Atari in 1982. In an unusual move for Atari, the 5200 version of the game is different from the 8-bit home computer version of the game. In many ways, it's an improvement. Though the graphics do not come any closer to the arcade, the gameplay does. Shields are present, and even though the invaders march on to the screen from the left, there is no "mother" invader present on the screen.
Atari 400/800/XL/XE
Developed by Atari in 1980. Generally speaking, the Atari 8-bit line of home computers were considered homes to many accurate arcade conversions, but this version of Space Invaders diverges the most from the arcade version compared to any other Atari conversion. No shields are present, and there is a kind of mothership present on the side of the screen that the aliens appear from.
Game Boy & Super Game Boy
Original Gameboy version developed by Taito in 1990. Reprogrammed for the Super Game Boy by Taito and published in the U.S. by Nintendo in 1994. When accessed through the Super Game Boy, two modes are available. There is the Super Game Boy enhanced mode of the original Game Boy version, but the game also contains a full Super Nintendo program that is identical to the SNES entry below.
MSX
Developed by Taito in 1985. A near pixel accurate conversion of the true-color version of the arcade game.
NES
Developed by Taito in 1985. Not quite as pixel accurate as the MSX conversion. All invader sprites were forced to fit inside of the Famicom's 8x8 pixel tile size.
PC-Engine CD
Published by NEC Interchannel in 1995. By all accounts, it is similar to the SNES version, including the two player competition mode.
Sega SG-1000
Developed by Sega in 1985. A near pixel accurate conversion of the true-color version of the arcade game, although with a slightly different color palette for the aliens.
SNES
Developed by Taito in 1994. Republished in the US by Nintendo in 1997. This was the first conversion of Space Invaders to provide players with the option to simulate one of four different varieties of the arcade machine. Players could choose between a black & white mode, color back drop mode, color celophane overlay mode, and true color mode. Additionally, there was a two-player only competition mode. This conversion served as the model for most future releases.
Wonderswan
Developed by Taito and published by Sunsoft in 1999. Pretty much a straight pixel accurate reverse black and white conversion like the original Game Boy conversion.