what he meant is for the investor to compare it to previous sales of GTA they have to compare the attach rate... which make sens to me..... if you have 40 million console and sell 15 million games.... and you have now let say 20 million and just sold 10 million.... you still did a better job promoting and selling the game with the 20/10 result than the 40/15.....
of course in terms of profit you look at sales.... but success I can see how you can consider the attach rate...

So, by that logic:

 (1.93 + 15.41) / (117 + 24) = 17.34/141 = 12%.

 Therefore, anything above (.12 * 30) = 3.6 million is successful (higher attach ratio than PS2 + XBox)?

I could agree with that, but I doubt Take 2 or the analysts would...

yeah in terms of sales yes... of course they do look at that.... profit is another story.... they won't make as much profit than previous gen for 2 reasons... 1 install base.... and 2 the production cost is probably way higher than it has been in the past....

now you are an investor you look at profitability... but to say you did a good profit against a bad one or a loss you take in consideration the attach rate.... they will make a profit anyway... now to compare it to last generation you can't do without the attach rate.... and that's why that dude says it will be more important to judge that this generation.. because it's almost certain they won't reach the sales number of last gen in 2008.... but might actually have better attach rate... this would make the investment virtually more profitable taking in account the install base....

when you invest you have to take that in account...