I've been thinking that GTA IV only has to sell as good on 360 as PS3 in order to be considered a success.

Given that the franchise pretty much defined the playstation and it has never shipped on 360 at the same time as playstation I don't think anyone at Microsoft believes it will drastically outsell PS3.

I know it has exclusive content but I think that just levels the playing field as most die hard GTA IV fans won't believe that it will have more content on 360 than PS3.

Anyhow...  What do you think?

Success is too subjective a word. We can talk about at least two different kinds of success:

Financial success: From Microsoft's and Rockstar's point of view, selling on par with the PS3 would be more than enough for financial success. Even selling half of PS3's version would be a financial success I think. Rockstar would probably have gained userbase which wouldn't have gotten GTA4 if it wasn't on the 360, and Microsoft would get money-conscious customers' money.

Competitive success: The 360 is still on top by a wide margin, which means that if hardware 360 sales are as big as PS3's during GTA4's launch period, this advantage will be maintained. This too would imply a very significant competitive success, for which even a smaller margin would be enough.

There are probably more kinds of success which I'll leave for other people to think about since I'm feeling lazy. Considering these two kinds of success together, I'd say having 33% of GTA4's sales could well imply success already, while selling 40% would definitely do so.

PS: We can also talk about the regional perspective, from which Microsoft would like to steal as much userbase as possible in Europe, which is still seen by many as Sony land in terms of consoles (although it only applies to HD consoles now).

8 million

Double what it sells on PS3 to be the success that Microsoft wants it to be. Only selling 'on par' with the PS3 version despite having sold 7 million more units and having the extra $50 million spent on it would be horrible for MS.

As opposed to how much on the PS3?

But the game will sell well on both console
80% of the sales will be done by PS360 PRESENT owners
20% by NEW owner

whatever GTA4 succeed to increase hardware sales or not, it will primarly sell to PRESENT owners. Considering the hardware base, it is OBVIOUS Xbox360 version will sell more and will be a success

Over 9000!!

But seriously, I think, considering the far superior userbase, and all of Microsoft's invested money/efforts, it should, by all means, sell at least as good as on PS3, perhaps even better, even though the last few games were on PS2 mainly.

GTA needs to sell by at least a 2:1 to be considered a success , they payed $50 on exclusive content , proly 10-30 on promotion and with the significantly larger install
base anything under MS's 6 Million:PS3's 3 Million would be considered a faliure in my eyes from a competetive perspective , they'd still be raking in the cash though , so it's a success in that respect.

MS success would not be measured by the software alone.

It would be based mostly on an increase in hardware for the 360 and it would have to be much higher then the PS3's

why?

Well because MS spent $50 million on extra content, so if the PS3 gets a bigger boost in console without spending a dime then MS will look like ass's.

well, sell more than the ps3, it's kinda obvious.