The question is if GT is as popular as it used to be. I was really into GT1, 2 (especially 2), and 3 but after that it didn't hook me like it used to. I still think it's gonna be huge in Europe, but i think it's not gonna sell as much as it used to in NA and Japan and that will be the deciding factor.

Halo is at its peak right now and it is showing legs. I'm gonna go with Halo edging it out by a million or so.

The bolded is wrong.  FPS usually sell way more than racing games (GT is the exeption to this rule)

But tbh i really don't get your NA vs the world stuff or what it has to do with GT5 outselling halo 3.  

past GT's usually sold about the same in NA and EU (sans GT5: Prologue, and GT4)

But we shall see which one sells more.  I would expect GT to sell at least 3.5m first week for it to outsell Halo 3 LTD.

But i'm goina predict First week will be 2-3m max.  

But like i said i think GT will come close but unless its heavily bundled, i don't see it outselling Halo 3

Nope. Anyone who thinks otherwise is living in a fantasy world.

Remember the GTA series??? It was more popular GTA>GT on the PS2 and look how much it sold on the PS3

What you can't understand the differance that it was exclusive now multi ? there was no other option to buy it.

Its not rocket science.

The more i look into the sales the more i think what i believe what i said.  GT has been lowering in sales since it started in Japan with GT1 selling the most by quite a bit.  Whether it is gonna outsell Halo is gonna depend on NA, i really expect sales to continue to slide in Japan.  I'm sure it's gonna be big in Europe, even 4 sold almost as much as 3.  I can see it selling 5 million or more in Europe, and around a million in Japan, but whether it outsells Halo is gonna depend on whether NA can sell on par with europe or not.  The GT games that sold huge numbers actually sold more in NA than in Europe. 

FPS sale way more ? really do check some numbers.  You might want to take a look at Need for Speed sales for last gen, to bad they have run that franchise to the ground.

4 of the top 10 PS2 sellers are racers, thats what majority of the market chose as its top sellers last gen.

GT3 1.89 million.

GT Concept - 0.43
GT4p - 0.79
GT4 - 1.16
= 2.38

No GT is not declining in Japan, strong as ever.

Lack of online really hurt the final build, theough Europe will eat it up no matter what it seems.  GT4 undersold due to online being cut, that was to be the big reason to upgrade from GT3 it really hurt its sales.

Now look how nuts about GT Europe is.

GT Concept - 1.13
GT4p - 0.57
GT4 - 5.73
= 7.43

Now think what full GT5, online Top Gear test track more Euro Excotic (Ferrari) will do. 

And crazy thing is as great as GT is, there is plenty that can be made better.

Looking at GT2 and GT4. I say GT5 doesnt have a chance on a poor selling system. :)

Halo 3 is too big for GT5 to beat it, especially with the PS3's install base.

well its a sound guess, though look how much larger 3 was than 2 for halo.

as for gran tourismo, 4 did worse than 3 so possible that 5 does worse than 4. especially considering the install bases. And don't bring up what instal bases were when released because ps2 was selling insanely faster.

so based on that, i'm gonna actually say no Halo 3 > GTA5
But wouldn't be surprised or care if otherway around