With the ever increasing craze and excitement around Gamerscore and Achievements, Microsoft have recently worked with their publishing partners to implement some new policies for new games coming out. Here are the basic rules:
1. All regular disc-based games MUST have 1,000 Gamerscore in the base game. This means that any consumer who buys a retail game will have the opportunity to unlock the full 1,000 Gamerscore without having to pay for any add-on content. Note that a publisher may decide to deliver a portion of this Gamerscore via add-on content, but the add-on content will always be free to the consumer.
2. Game publishers will have the option to deliver another 250 incremental Gamerscore on top of the 1,000 via add-on content from Marketplace. This add-on content could be either free or paid. So if you complete a game and earn the full 1,000 GS, you could by getting new add-on content earn up to a total of 1,250 points from a game.
3. Xbox Live Arcade games will operate in similar fashion, but given the size of these titles they will allow you to earn up to 200 Gamerscore from every game and up to another 50 points from add-on content.
http://gamerscoreblog.com/team/archive/2007/02/01/540575.aspx
