Yes go buy a 360 right now! You'll love it!

 Yes! Lets change the entire scope of the conversation from what's currently out to planned future projects leaving out any upcoming sandbox games for the 360! Magnificent!

Or you could just count the number of sandbox games on the 360 and PS3 as is, and assume both will get new ones at a similar rate (which they will). After all, you failed to list exclusive sandbox games on the 360 :) 

@RocketPig

The PS3's has the best "Hasn't Come Out" Library in the WORLD!!ZZ!!!

We must all bow down to the PS3's upcoming games!!!

@Halil23

A gaming console shouldn't be an investment for the future.... It should be an investment for this weekend when it rains.

Don't listen to anyone here...they don't know anything.

If yuo have the money and want to play the game buy the console the game is out for. I bought the gamecube for resident evil 4 and don't regret it at all.

Life is short...play what you want to play. And seriously, if you can't find the 360 fun after gta4, it may be time to re-evaluate your standards in gaming.

I agree with the sentiment that a console should not be purchased for a single game. However most posters telling you this are doing so with impure motives. Were the game exclusive to their platform. Then it would be ample justification in their point of view. Basically it is a fool proof argument used to attack a potential purchase, and nothing else.

Looking at the 360 as a whole however indicates that it is a good purchase. The price is reasonable. The console has the larger library, and the larger must have library. The console has the more varied library. The interface is more conservative, and your going to get to play most multiple platform titles of existing franchises. So you would do pretty well with the purchase. Especially if games like Grand Theft Auto appeal to you.

Make an informed decision.

Look up the 360 library of games, check the prices, look at what the competition is offering, then make a choice.

Taking into account that you have a good gaming PC is very important, sadly people here are ignoring that comment.
Eg. Gears of War and Bioshock are both out for the PC so they can't be counted as reasons to buy the Xbox360 and UT3 isn't a reason to buy a PS3 ect.

@ OP
I think Twestern has a great system for this
If the cost of all the games you want to buy for the Console  is greater then the cost of the console it's self then buy it.

if ∑G > C then

Buy = true

Else

Buy = False

End if 

Another thing you have to decide is if you don't mind using a gamepad for the games your thinking of getting.

In the end GTA4 is most likely will be released for the PC, will be cheaper and might look even better on your powerful computer.

Thinks style of above response is funny ^^^

I think one game is insane to buy a system for ,,but still not far from reality


off topic: just wondering why you are not considering a PS3 ?

Did you really just call mrstickball rocketpig?