This.  HW and SF both matter. 

Like some other people have said the measure of it's success will be more hardware related than software. This is their tentpole title for the first half of 2008 so they want it to help increase console sales.

as long as they sell enough to stop EA from buying T2, it's all good, ps3 owners gotta do their part too though.

I think that GTA IV's 360 version will sell more because 360 owners love achievements that up their overall gamer score. I'm still torn which system to get it for. I love my 360 but the fact that it used to be a Playstation exclusive has me swaying that way because of controls the controls on the PS3 will be virtually unchanged from previous versions.

I think to be considered a success on the 360 it has to outsell the PS3 version.

perhaps then, we should wonder...how much more will sony have to sell, than microsoft, for them them to have "success". if its less or par, i would consider that a fail for them.

 MS paid an extra $50 mil for GTA4, has a larger user base and is spending millions on ads so they have the most to lose.  Sony did nothing for GTA4 and seems not to care.  Don't derail the thread.  Want to troll then go away if not make a new thread about your question.

I believe Microsoft's REAL intention was not to sell more than the PS3's version but to STEAL away potential buyers from the PS3. Yes, Microsoft is out $50 mil but as long as they have at least 30% of all total sales as Sony had probably 100% sales in the PS1/PS2 eras, then taking market share from Sony might not be such a bad thing. Sony makes LESS money and Microsoft MAKES money.

Now as Microsoft payed a hefty fine so I'll go out and say if they sold 1-2 million more or less than the PS3's version than it's mission accomplished for Microsoft.

Both sides (PS3 / 360) have advantages and disadvantages that could even out the amount of sales for each consoles.

360 PROs - bigger userbase, most affordable console, and DL content
PS3 PROs - bigger FANbase, franchise is more well-known on a PS console

360 CONs - PAYED to have content in first place, HW unreliable
PS3 CONs - console less affordable, no DL content, and smaller userbase

If there is anything else or if I'm wrong then please add!

^ I don't see how the part I bolded will have any impact in sales.

 I thought of that as well and really should not have added that in first place.  I really couldn't think of any CONs for the 360 except the HW really.