A Steam member made a complete list of the games that are included in this collection. I noticed that the infamous adult 2600 video game "Custer's Revenge" wasn't included. Even if it was added as an adult DLC, its controversial sale would probably be protested by Native American rights groups, the NAACP, the ACLU and others as it was when it was first sold in the US back in the '80s. Not surprisingly, the original Atari 2600 cartridges are going for hundreds of dollars on eBay as sometimes controversy generates collectability for questionable items.
Well, not every Atari game but most of them, at least. For example, they didn't include three of the best Jaguar games, Alien vs Predator and the Iron Soldier games.