GT5 two year headstart and lower price-tag does gives it a major advantage over Halo 4, so im going to go with no.

You act as if Halo 4 isn't going to get a price cut in the next year or two.  Also, this is to see who comes out on top, not who gets to, say, 10M first.  So, the headstart doesn't really mean anything in this comparison.

@ OP

I'm going to go with GT5.  It should continue to have great legs for another year or two.  It also should have a pretty good holiday ths year, especially since it was only $10 on Black Friday, normally $20.  I already own a copy, but decided to get the XL version for all the DLC. 

Also, I'm actually somewhat surprised that GT5 sold so well.  It seemed like it took forever for them to do an official price cut (not sure how this compares with other GT titles) and Sony didn't seem to bundle the shit out of the game ike they have with previous GT games.

Update incoming...

Gran Turismo 5:

Halo 4:

Aligned launch chart:

As you can see, Halo 4 is at 5,158,526 after 3 weeks on sale and is currently tracking 1,409,923 ahead of Gran Turismo 5. Interestingly, Gran Turismo 5 sold more in its 3rd week on sale than Halo 4 did (672,202 and 607,817 respectively...So GT5 sold 64,385 more). However, this is explained by the fact that GT5 launched at the peak if the Christmas sales period and subsequently followed different sales trends than Halo 4 will.

According to my Halo 4 predicted sales chartz thread, Halo 4 should sell 395,200 worldwide next week.

Quick question.

Didn't GT 5 have a couple of different versions and if so are those counting for GT 5 sales?

No sure what you mean by this... Are you talking about GT5: Prologue? If so, then no. It's a completely separate entity to GT5

Well that is what I was wondering if that other version of the game was included because I am sure if Halo 4 did that, which they never have, it would help with sales.

Standard Edition, Academy Edition, XL Edition, Signature Edition and Collector's Edition.

Do all of those version get counted into the total sales gor GT 5?

EDIT: I know the collectors edition does because that was out with the regular edition of the game. However I am still wondering about those other version and if they are counted.

They would still be included in GT5 overall sales.