"Titles for Xbox 360 must ship at least simultaneously with other video game platform, and must have at least feature and content parity on-disc with the other video game platform versions in all regions where the title is available," it reads.
"If these conditions are not met, Microsoft reserves the right to not allow the content to be released on Xbox 360."
This also applies to Xbox Live Arcade games. Other Online Content "must simultaneously release on Xbox Live Marketplace in all regions where the game is available". Any demo on Xbox Live Marketplace "must ship within the same week of its launch on other video game platforms or via magazines".
Sony's policy, however, appears to be more relaxed. Generally, games that launch on Xbox Live Arcade first eventually emerge on PSN. Limbo, Castlevania: Harmony of Despair and Lara Croft: Guardian of Light are just a few high-profile examples.
While Lewis refused to rule out the possibility of publishing downloadable games that launch on PSN first in the future, "I'd be surprised if we saw that as something we'd encourage," he said.
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Not all agree, however. One representative from a publisher who wished to remain anonymous told Eurogamer Microsoft's policy blocks developers from taking advantage of other platforms' strengths.
"Microsoft is suggesting that anything but parity will result in them not carrying a title. They may think this is competitive, but it's not. They are killing any creative exposure of titles to make up for their own platform's shortcomings."