Looking first just anecdotally at Amazon to provide an illustration, both PS3 consoles and 360s are doing much better right now in the video game sales rankings on Amazon than they have been in the recent past.  At the time of this post, PS3 is ranked as the #6 bestselling item, sandwiched right between the Wii and the Wiimote.  360 is doing much better, too, up to #47 from where it had been in the 50s-70s for the last few weeks.  Both versions of GTA IV are in the top ten and probably won't be going anywhere for a while.

With the larger 360 install base and higher attach rate (lots of PS3 owners bought them in large part for Blu-Ray), GTA IV game sales will of course be higher on 360, at least for a year or two.

But what about the GTA IV effect on sales of the consoles? 

Will consumers (including 100 million PS2 owners) use this opportunity to swarm to PS3, with its extremely bright outlook and obvious longevity as a console and CE device?  Or will they see GTA IV as a reason to buy 360, when they may already want to play Halo, Bioshock, etc.?

Will the other games coming out very soon on the respective consoles have an effect? :

April/May/June PS3 exclusive heavies - Gran Turismo 5 Prologue, Haze, Singstar, Metal Gear Solid 4

April/May/June 360 exclusive heavies - Ninja Gaiden II, Unreal Tournament III, 2 Atlus games (?)

Will new SKU's/bundles/prices change the game?  Ah, good times lately in console land.

GTA 4 will be a big boost to sales of the PS3 (people know the playstation versions of GTA) and a smaller boost to the 360.

This game is nothing but good for both systems, I cant believe that by the end of this month GTAlV will be in my Ps3. :)

Why you want other GTA, almost every PS2 owner have the three version in PS2(GTAIII,GTA: VC and GTA: SA)

OT: I see a 20% boost for both consoles. 

I think that 360 will get more GTA IV sales, but PS3 will sell more consoles. Everyone's a winner. ;)

Unreal Tournament III 360 Exclusive? It's already out on the PS3 and has been for 4 months...or am I misreading your post?

probably will move more ps3s than x360s. many people who havent bought a next gen console would probably associate gta4 with the playstation brand as it has been available on the playstation in the past. not that the x360 wont have a boost.

but brand recognition helps a lot. for example, here where i live, if you want a soda, people say coke even if their buying a pepsi. people say colgate when buying toothpaste even if their buying another brand.

 ecxept Nintendo :)

It will move more PS3's than 360s, due to brand regocnition, but will still sell more of 360

 nintendo has mario kart. Everyone's a winner