The standard of all new releases is going to be good. Modern Warfare 2 will be a great seller as will Assassins Creed 2. Fans of Left 4 Dead will definetely buy the sequel. Looking to late next year Halo: Reach will be another great seller in the Halo series.
The reason that PS3 will sell more is because it is cheaper now. The Xbox's downfal is the little number of new features. However Sky Player has now arrived on Xbox 360 and hopefully that is the start of a number of new features. Game exclusivity has nothing to do with it, both consoles are equal there.