Losing those dedicated 3rd parties would happen eventually and it pretty much started with MS. MS paved the way for 3rd parties to make even more money. So why remain exclusive? Nowdays only a few companies can remain exclusive to one side or the other, because not only would they risk losing sales, they would also risk loosing money if the platform they betted on with their exclusives, didn`t sell enough to even profit.
As for Sony`s line-up. It`s evident that none of them, besides GT, is a match to a Halo/Gears of War or Mario/Zelda. But you also need to remember that most of Sony`s franchises you mentioned were created this generation.
Still. even, if Sony`s don`t have that impact per se, they exist in number enough to atract a lot of gamers and that might make up for the impact of Nintendo and MS´s big guns.
However, no one knows where the next Halo or Mario will be born. Could belong to either of them.
