let's start with the fact that we can't list Prologue as example of future GT5 sales

- it was the first racing game on ps3 except crappy F1 game, Ridge Racer(and those are very niche titles plus ps3 launch games) and very average Motorstorm,

- it was budget game,

- it had no competition for what 4-5 months before release and something like 4-6 months after launch,

now

- past GT games success was because casual gamers,

- there wasn't any awareness of competition(especially during psx life and early ps2 era),

- you could pretty much get either NFS, Ridge Racer or GT game in the past,

- ps3 doesn't have diversity if we're talking about audience(it's all about shooters and action games now),

- with exception of first Motorstorm(which sales come mostly from bundles and sequel flopped hard compared to original), last 3 NFS games, Midnight Club, Burnout Paradise and Grid nothing really sold well on ps3 if we're talking about racing title,

- most racing sim fans already chose their console and series to follow - that's Forza, just look at the sales of Forza 1 and 2 on simillar userbase.

Forza 1 sold 1mln copies, 

Forza 2 sold 4mln copies,

Forza 3 sold 2.3mln copies in first 24 weeks - more than 80% better than Forza 2 in first 24 weeks.

- there's too much competition and people gone away from games like GT to open world and arcade racers,

- people are tired of waiting and already bought 360 because of Forza series or other racing games,

- demo gave really bad impression of full version GT5 and Prologue showed that Polyphony is far behind developers like Turn10,

- there will be released 5-6 high profile racing games before GT5(if it comes this year of course),

GT5P will have passed 5mln by the time GT5 releases.

GT5 will sell less than its Beta?

can it sell that number again the day after he quits? :D

Instead of finding counterarguments to the aforementioned points, I will simply say why I think it will top that.

-It's the first FULL Gran Turismo game on the ps3.

-It will be marketed like Crazy since it's Sony's Biggest franchise.

-It will be bundled like crazy for the same reason.

-(If) it is released in Fall.

Those are enough reasons why it will sell more than your expectations..

Waron does have a very good point - a lot of Sony fans have made arguments along the lines of "GT5 prologue has sold x times as many copies as this other prologue, thus GT5 will sell x times as much as that full game"

Which is a terrible argument for all the reasons waron mentioned.

I don't see where the rest of his conclusions are drawn from though

Its will sell over 10 million

Well the userbase argument doesn't work for openers. Obviously, smaller userbases with popular brands just means a more concentrated base for the game which leads to bigger openers. Such as the case for Halo 3 back on the 360 which had amazing attach rates. Or even Zelda: Twilight Princess launching on Wii with above 90% attach rate. GT5 will probably have a relatively big opener given that.

However, userbase does matter when we deal with "legs". Obviously the GT games are huge mainstream titles. And the longevity of the sales of the title could be affected by a smaller userbase. But we also need to factor in the potential of the game becoming an "evergreen" title or system mover. That could extend the life of the title.

It's hard to tell now if it will sell the "worst" in the mainline series, but I think given the past history of PS3 buyer trends, it should open quite well. I don't think it'll sell bad given the PS3's situation and possibly be able to go over that 10 million mark. Just going to need more info on PS3's state 6 months from now and a year from now which obviously I can't know until it happens haha.

EXAAAACTLY..thank you

it should sell between GT3-4

MGS4 did ? why this shouldn't?

What competition?

GT5 will have huge legs, won't do Halo or COD first week numbers, but it will be the highest selling PS3 game this Gen.