And King of Wale just demonstrated a case in point Rocketpig.

 17.22 million / 10.36 million = 3, and 2 + 2 = 5 right?  

 All developers care about is cash in their pockets, so wherever you can move more raw units is where you will focus.  In the PS3's infancy this was all about the xbox 360, but as more and more consoles are sold I see 3rd party devs moving away from exclusive games entirely in favor of multiplatform so they can sell more.  

The only developers of exclusive games in the future will be in house studios, or ones where Sony/Microsoft/Nintendo own huge amounts of stock. 

I think the 360 might see a spike in sales when GTA comes out, but nothing in Halo 3 levels. Other than that, I can definitely see the 360 going downhill significantly in terms of sales throughout the year until Gears 2 comes out. Personally, I think the 360 is going to = PS3 in 2007 this year in terms of sales and amount of really popular software releases. I honestly think Sony can match the 360's 2007 success.

I think Microsoft may need to shell out a lot of money on the GTA campaign, though. If Sony manages to convince Rockstar to run the Playstation 3 logo splash after every GTA commercial, PS3's may fly off shelves faster than 360's.

You win, topic over.  Raw sales only matter as long as the companies think that the sales trend will continue in the future.  EA has already stated that they think that will not be the case, and so they have committed themselves towards efforts that will make PS3 a more important part of their development (and leading with it, because it just works better that way).  It takes a year to make a game, so why in god's name would these companies not be looking at where the games will be selling a year from now?