Atari itself bears much of the blame here. It marketed its console as the Atari Video Computer System (VCS) and later as the Atari 2600. In Sears' department stores the console was called the Sears Video Arcade, and while the label covering the switches may have been different, underneath they were exactly the same system as the Atari-branded system being sold in non-Sears stores.
Similarly, Atari allowed Sears to sell Atari's cartridges under the Sears Tele-games label. Thus each game would have two releases, and the names would not be the same but the ROMs would be identical. Thus the game Atari called Breakout, Sears called Breakaway IV, Circus Atari was shortened to Circus, and Outlaw became Gunslinger. Sears' actual contribution are three games Atari never released under its own label.
In addition to the Sears license, Atari kept most of its early titles in circulation with corresponding differences in labels. Space Invaders has a text, picture, silver and red label, but it should always be counted as one game. Sometimes games would be renamed, as Hunt & Score was renamed to A Game of Concentration and also released by Sears as Memory Match. Finally, Atari did release games in its Red Label era originally published by rivals in the pre-crash era such as Coleco's Donkey Kong & Donkey Kong Jr.
Pepsi Invaders and Atlantis II are variations on the originals and were provided only to a select few, so I consider them as to prototypes, and they should not be counted in an official list of a system's games. However, there are several other extremely rare games like CommaVid's Video Life, only available to people who purchased the MagiCard. Essentially it would have been purchased only by the few of the few. And then there were games like Birthday Mania, sold only in a limited geographic area and so rare that the ROM has not been dumped. Unlike Pepsi Invaders and Atlantis II, they are not hacks of existing games, so they are included. While there are several games that are very rare, they were at least available to the general public, usually only via mail order. However, even if included, the final number would not significantly change.
Two issues with a list of North American Atari games is that games only released in PAL territories must be weeded out. Prototypes and reproductions should also be filtered out. The final number is focused on games released during the console's lifespan, so homebrew games are not counted. What games were released in North America is mostly well-known, but when you go to the many European countries, South America and Taiwan, the titles really start to become difficult to manage. If pirate cartridges are considered, the PAL territories probably had more games released than the U.S. and Canada, where relatively little piracy occurred.
Finally, games released by pirate labels, which frequently only rename the game, should also be left out unless that has been confirmed as the only a game found a North American release. Thus most, but not all, releases by Zellers should not be counted. Cartridges that are not games like diagnostic carts, copy carts, rewritable cartridges. Nor are the Gameline Master Module or the Starpath Supercharger counted, but the former allowed exclusive access to Save the Whales (included under 20th Century Fox) and the latter came with Phaser Control. The term "game" is liberally interpreted to include any kind of cartridge or cassette software intended to have some kind of entertainment or edutainment purpose. Carts like Basic Programming, Music Machine and MagiCard are thus included. Double-ended cartridges are always counted as one game so long as one-half of the cartridge was not released as a single game. Virtually all the games so released were also released as single cartridges. Here is the Tally :
|Atari, Inc. / Sears||101|
|20th Century Fox||18|
|Arcadia / Starpath||11|
|Selchow & Righter||1|
|Personal Games Company||1|
|First Star Software||1|
|Total Unique Games||436|