Since you have a PS2, the obvious choice would be to get a PS3 ! Both GTA 4 versions on the PS3 and 360 are superior so by choosing either version you can't go wrong !

PS3 mate you cant go wrong

YOU CANT GO WRONG

I would definitely vote xBox 360 but that's just my opinion

I would get a PS3… a lot of people are going to tell you to get a 360 just because it is more popular but the PS3 is a stronger system. It has better graphics with blueray (although GTA IV looks pretty much the same on both). Also the PS3 has free online, internet and it is a lot less noisy than the 360. The 360 ends up sounding like a vacuum when its on lol. Another thing is the 360 can get "the red ring of death" which will completely kill your system. In the long run I think that getting a PS3 would be better.

The price is the only difference. GTA 4 runs exactly the same on both consoles, though the controls of certain things, like helicoptor flying, can be more complicated on the PS3. The controls on the PS3 for helicoptor flying is called SIXAXIS and is very complicated. My opinion, go with the Xbox 360.

xBox 360 all the way, I heard and see the PS3 is a bit laggy in certain areas of gaming. I would suggest the 360, yes their are pros for the PS3 such as Blu-Ray etc. Graphics are basically the same.
Good Luck!

graphic wise,both consoles are nice.
Pricing wise,xbox360 is :-
1)cheaper
2)can be modded to play pirated games
3)pirated games are cheap to buy
4)u can download xbox360 games n burn into dvd9 for playback.(modded only)
5)Well established online service.

since u already have ps2,maybe u would like to try different console? I have ps2 too…DS & crappy psp.

PS3 ALL THE WAY! DO NOT GET A XBOX360 THEY ARE CRAP!
play station has been better for ages.

Get the PS3 because it has so much better griphix and gameplay. It uses blu-ray technology so it can hold more graphic details and has high-definition gaming. It can also hold longer and better games. Also, the controllers are a lot easier than Xbox. The Xbox controller is not a great shape for your hands. The PS3 controller sits in your hand easily and comfortably. Another great thing about the PS3 controllers is that they have motion sensors (you can tilt the controller and control planes, dragons, etc. and shake the controller to get fire, monsters, etc. off of you. The games are just flatout more realistic too. As I mentioned, it has blu-ray technology so the games seem to have depth and you actually believe they are real. In car games, the cars look real. You cannot get a better system for gaming than the PS3.

Oh my gosh these questions come up ALL THE TIME!

just get a PS3…you seriously cant go wrong and if you do…sony repairs it for you like super quick and for free if you still hav your warranty.

its got better graphics, better games coming soon (like MGS4!! CANT WAIT!) and easy to work with, internet browser, ps3 home coming soon as well (youtube it)

If you are getting a new system for GTA IV, I highly recommend getting an Xbox 360 (although I will probably thumbed down to oblivion for this in the PlayStation area here).

But the reasons are simple:
First of all: The Graphics on the Xbox 360 are smoother than on the PS3.
On the Xbox 360, edges have a less noticable jagged effect than edges on the PS3 have.
That's because the PS3 version of GTA only displays 640 horizontal lines and the Xbox 360 displays 720.

Then in September there will be additional download content for the Xbox GTA IV, that supposedly is compareable in complexity to Vice City and San Andreas compared to GTA III.

In regards to gameplay both consoles are completely the same.
However on the Xbox 360 you can always bring up your buddy list during the game and chat with your friends. This will be only possible on the PS3 with a future update.

Also, you will be able to replace any game's music with your own music on the Xbox 360 (the console will however keep the sound effects, so you will still know what's going on in the game). Your MP3 Music can come from the consoles harddisc, your USB drive, or your networked PC.

So in short, get a Xbox 360 for GT IV.

And to comment on a few misconceptions in other answers here:

@Mini:
The Xbox Controller battery lasts for over a week on my console with daily gaming sessions of over 3 hours.
The Xbox warns way ahead if the batteries are only half full, so you have enough juice to finish your gaming session fo the day, and then put the battery in a charger overnight.

Also, the 40GB PS3 model is NOT able to play PS2 games at all.

@PMS:
Keep in mind that most of the upcoming games for PS3 will also come out for Xbox 360.

@Dan
The BluRay format doesn't make better graphics. You just have to keep in mind, that the PS3's graphics chip is based off the NVIDIA 6800 chipset.
Any PC with a $80 grpahics card can outmatch the graphics of the PS3.

@SA_Chick
If the Xbox 360 breaks down, you call the toll free Microsoft hotline. You have a 3 year warranty on the Xbox 360 for the red ring of death error, and up to 2 years of warranty for other defects (depending on country).

The Sony service once denied a warranty repair, because the console was "dusty"

definatley 360 it over rules any day.