When people buy a new HD console, looking at the numbers after 26 weeks for CODIV - Still selling 100k a week and GTAIV, THE franchise of this generation amongst the HD systems there is a pretty good chance they will buy either one or the other or both. They are the games people know about, that their friends have and they're both known safe purchases if you want value for money.

 I don't think that the sales of either one of them are going to slow down substantially enough to prevent either from breaking the 10 million sale barrior. CODIV is just 10 solid weeks away from that target and another 2 million isnt hard to imagine by the end of the year factoring in holiday season sales.

As for GTAIV, its pretty self explanitory as people buy Consoles this is one of the must have games that people will play first. This games sales will be tied to the number of console sales. Its not that hard to imagine, for example Wii Play tracks close to Wii console sales. I don't believe that it will track as close but it will have very long legs and stay in the charts for a long time. There are a LOT of people who have played and loved this franchise and its not hard to imagine an atachment rate of 0.2 for new console purchases. Its a huge game, great value and they know what it is or they've seen it before. 12 million for this title will be an easy pick, 15 million would be my cautiously optimistic bet  and 18 million would be my caution to the wind bet for the lifetime sales. It will probably have another 2-3 million sales to current owners in it then the rest will come from new console buyers. 12million easy.

 Sorry, im not a good analyst but I hope its clear.

both are pretty much a LOCK to sell that much, so I don't get why you are even talking about it.

It's like predicting that R2 or GeoW are million seller

for some reason i dont think gta4 will sell more than gta andreas
and regarding cod4, if it retains the modern theme it will do extremly well but if it reverts to ww2 theme, although it will do well, it wont sell as much compared to cod4

still will be interesting to see how these games pan out

I think it goes without saying that they will sell 12 million.

 GTA andreas was sold on the PS2, when the PS2 had a user base of over 70 million.

GTA IV launched on a combined user base of only 30 million. hmmmm. 

Prediction: Guitar Hero III is going to beat them both in lifetime sales, revenue and profit.

I don't believe Call of Duty 4 will hit 12 million, actually, although I do think it will get close. The reason being that as soon as the next big shooter comes out, it will kill off the sales of the game. Good example: take a look at last year's charts and how sales of Halo/Call of Duty killed off the sales of Gears of War from the previous year. There are quite a few high-profile FPS games coming this Fall, including the next Call of Duty, so I don't quite see it happening. (This is in no way a knock on Call of Duty 4, which has been a humongous success by any standard.)

Obviously combined sales of Grand Theft Auto will hit 12m. It's a little too early to say if either platform will reach the mark individually.