The console wars are getting pretty brutal, most games tend to be spread across all 3 platforms, even Sony's GTA3 series went to XBox. However Sony still managed to get them to their system first with a mandatory waiting period for other platforms.
Whoever can can get the most exclusive games that are also good is going to have the distinct advantage. M$ has a chance coming out first to impress 3rd party developers to develop for them, but the exlcusive part is going to be hard to get.
Sony's had the advantage of being market leader, it would make sense for them to remain the market leader and thus wouldn't be too hard to convince 3rd party developers to be exclusive or promise delayed releases to other systems - however this go-round it seems that all the consoles will be very similar in terms of hardware capability meaning games should be able to be ported to all 3 systems. However Sony's system is probably most different from the others, having Cell and nVidia graphics, this is good or bad, considering their system might be the most different of the 3 to program for and thus could make exlcusive titles a sure thing, or developers to drop PS3 and release titles for Revolution and 360, although that's probably not too likely a situation.
Then there's Nintendo. If their new system can live up to its code name, Revolution, it could be unique enough to grab a lot of exclusive titles if only because the other systems can't support the special feature(s) Revolution brings to the table. However right off the bat thats a bad thing because it first alienates Nintendo, and seeing as how they're probably the biggest risk at the moment it will probably take some convincing on Nintendo's part to get early support, of which they're supposedly doing this by offering several revisions of early dev. kits.