I think you have it backwards, MS said HD-DVD will be for movies only. Sony has said that all games will come on blu-ray to prevent piracy.
http://ps3.ign.com/a...6/696057p1.html"March 14, 2006 - At its PlayStation Business Briefing 2006 held in Japan, Sony announced today its production plans for BD-ROM discs (Blu-ray). As it turns out,
all PlayStation 3 games will ship on Blu-ray to help prevent piracy. In other words, no "cheap" DVD releases.. Of course, the system will still play PS2 and movies on DVD.'