This is kind of like asking why Ratchet and Clank doesn't outsell true Mario iterations...

At any rate, a few reasons:

1) Gran Turismo is older. It got it's start 1997. Forza started in what? 04? Usually when the first killer app comes out, it gets the bulk of the sales. Look even at Dragon Quest vs. Final Fantasy - DQ was first, and sells far better in Japan than Final Fantasy does.

2) Gran Turismo was/is on Playstation. It's kind of hard to sell insanely well when your competitor (GT1) debuted on a system with 4 times the install base. That led to higher sales and a better market perception.

3) Marketing. Gran Turismo, due to reasons 1 and 2, is far more well known. Forza, although a better game, has an uphill battle when GT is known as the premier racing sim.

4) Competition. Correct me if I'm wrong, but Gran Turismo never really had any internal (ie, Sony-developed) racing IPs to battle with. In all actuality, Project Gotham Racing was Microsofts flagship driving IP (and before that, Midtown Madness). Forza has had to fight with PGR and other titles, while GT never faced such internal pressure. That allowed the GT series to flourish far quicker than Forza, which as debuted in a pretty saturated racing market.

Having said all of that, Forza definitely has the quality to go toe to toe with Gran Turismo. It's laughable seeing Sony fanboys argue that GT is the better series. If your comparing how "close" racing sims are to the real deal, Forza has always been the more realistic series in every way. Don't get me wrong - GT is an awesome sim, and GT got me into racing sims, but Forza tries much harder to be more accurate. And racers do use Forza just like GT to train on courses. So from that kind of a quality standpoint, FM can establish itself as a good alternative to the GT crowd.

Do people even realise that the motor industry thinks Gran Turismo is the most realistic driving sim? I think they know more than you.

I have played all the GT games and Forza 2. The cars drive so much more realistically and better in Gran Turismo.

mr stickball, gt5 is better,b the only ppl who claim otherwise are xbox gamers and no1 else. polophony are activly involved in the auto industry thier new similation is the best out there. everyone to thier own i suppose, ive tried forza and gt5p both on the susuka short and both withjh the same viper, the difference in the handling the looks and sound are better on gt5p

Yeah because we all know GT was never bundled....ZING!

Oh, So a few new cars and a couple of extra tracks make GT 4 stand out over GT 3 huh , yeah, I dislike sony but the bottom line is that GT 3 is better than GT 4 because GT 4 aside from a few more cars and everyones fave new snowy track brought nothing to the table....................

I'll give credit where credits due....... God of war, Metal gear solid ect, But the truth is that Gran turismo has been caught up in terms of great racing games and the only reason you still think its "untouchable" is because its a sony game........

Known sony hater yes, But theres known sony fanboys who hate Microsoft so why should anybody listen to them? Its called an opinion.....................

And lastly you are a stern supporter of Sony and Nintendo and you advise people to boycott Microsoft so why should anyone listen to you either?

I have never prior to today said anything like "why should anyone listen to you"

But today i have made an exception just for you

Let people have an opinion and chill out huh

Pretty simple.

It's not as good.

/thread?

It's the same reason why NFL2K5 failed to outsell Madden 05! It's all in the brand name sometimes.

they aint getting closer in quality!! GT kills forza in every way!

yep! even GT5 prologue can outsell all other racing games!

im sorry but forza comes no where near GT5! i can safely say forza COMPARED to GT is absolute shit!