Its always about the past with this type of stuff...

Assuming that GT3 is an outlier, Gran Turismo if going by past trends will sell 10M since all the other releases cluster around that point. Halo 3 will sell over but not significantly more than 10M.

At this point you can probably say that Halo = GT without any more data. Im ignoring userbase and just focusing on an assumption that GT5 will sell around what pretty much every other GT game has sold which is about as much as Halo 3 has sold.

1) Is it really fair to give Halo 3's attach rate 2 years after its release?

2) You doubt GT5 will sell 7.5 million? Seriously? o_O

3) Halo 3 will definitely not stay at a 33% attach rate till the end of the generation- assuming a pessimistic 60 million sales of the 360 LT, Halo 3 would need to sell 20 million. Not happening.

EDIT: To sum it up, right conclusion, wrong methodology.

1. No.

2. You doubt it in your heart.

3. What, no hyperbole from the big Xbox 360 fanboy on the scene? I must say im impressed.

Attach rate is completely the wrong approach here IMHO. That is looking to the importance of that game to the console, but I think if you're talking 'bigger' then raw sales units is the measure to use.

A console could sell 10M units and have a game so popular with the demographic for that console that it sells 8M on the console - wow an attach rate of 80%

Another console could sell 100M units and have a game that sells 20 M units - gee, only a 20% attach rate.

However, the former game is obviously more relevant for the first console, however, with an additional 12M in sales, the second game is clearly the more popular overall - or bigger franchise - as it reaches more individual people.

Halo is a big franchise, and for Xbox its a massive franchise - so important I believe both the Xbox and 360 couldn't have survived without it.

However, a franchise like GTA is clearly more popular as its total unit sales far exceed Halo, for example. And the Mario franchise is clearly much larger than Halo.

As for something like GT, well, I think total sales of all games to date are probably higher than Halo, but then there have been more GT games (GTA too for that matter).

Then there's the complication of exclusive vs cross platform. Halo is exclusive, as is GT, but GTA is not.

In the end there's lots of ways to play with the numbers, but what I think everyone is fumbling around here is the following:

1) no Halo isn't the biggest game franchise in history

2) yes, it is by far the biggest franchise on Xbox and the most important

3) yes, there are other exclusives that are larger franchises, but only a few, Halo's in the top ranks too so relax

4) yes, one of those franchises (GT) is on PS3 - just relax, Forza's great too, and maybe over time Halo will overtake it (after all it trails in games released currently)

Time will reveal all. GT5 releases and how it impacts on PS3 hardware and how many copies of GT5 are sold over time.

Minimum GT5 lifetime sales estimate = 10 million
Maximum GT5 lifetime sales estimate = 15 million

Looking at the last Grand Theft Auto game having sold 17.89 million copies on PS2 and the current one at 5.69 million (a difference of over 12 million) it really makes me wonder if the PS3 can deliver massive sales in the 10+ million range. Some people point to smaller franchises that sell better than previous installments but none of those are of the scale we're talking about in this thread.

Gran Turismo franchise shiped 50 million copies
Halo franchise shiped 24.8 million copies

So, GT>>Halo, its easy

@ Numonex - Are you feeling Ok?

Although highly unlikely, its still possible.

Nobody knows how well PS3 will do when it reaches a good price for consumers, and IF it starts to take off like PS2 did, 15Million is possible for a Gran Turismo.