BIGVIP over at the Gamerscore Blog wrote up an article discussing what they've done for the gamerscore system on the 360. Microsoft has talked with developers and set clear rules pertaining to a game's gamerscore. All games here on out will be required to offer 1,000 gamerscore and all arcade games need 200. No part of the gamerscore can come from purchased XBLM content, but free downloadable content is fine. Also, any new expansion packs or new downloadable content can offer an additional 250 gamerscore for normal games and an additional 50 for arcade games.