PS3 already lost Assassin's Creed, Virtua Fighter 5, Armored Core 4, Fatal Inertia, Bladestorm, as Grand Theft Auto 4 as exclusives. (all coming to the 360) Now they're looking to lose Tekken 6 as an exclusive as well.
MS snagged the rights to Splinter Cell: Conviction, Mass Effect, BioShock, Lost Planet, Blue Dragon, Gears of War, Lost Odyssey, and Dead Rising.
Guitar Hero II is now coming to the 360 with extra songs/features.
And, rumors are, that Sony might be losing Devil May Cry 4 exclusivity as well. We also know that Resident Evil 5 will be appearing on both the 360, and PS3. As will many other big titles, like Mercenaries 2.
Metal Gear Solid 4 so far (as acknowledged by Kojima/Konami) is coming to the PS3 first, but they have not said it won't come to the 360 ever. We've already seen other Metal Gear titles on the Xbox, and Gamecube.
Sony still does have some of it's big ffranchises in lock though....Gran Turismo, God of War, and Final Fantasy. To name a few. But, it's no secret that they've been losing some BIG titles. Part of that has to do with the cost of developing games for these new consoles....developers are starting to have to go cross-platform to enable them to make enough money to profit on their titles.
Sony also dropped the ball with some developers, like Rockstar, Take Two, and Ubisoft. Living them hanging....basically costing Sony the chance to get exclsusivity.