Starcraft 2 Wings of Liberty. Just because every South Korean is going to buy it day 1.

I'm thinking Super Mario Galaxy 2 will be the best seller, followed by Halo Reach..

Though neither of these will be the best game.

Apparently Wallmart and Amazon are doing the old $20 gift card when you pre-order Halo Reach. That will just strengthen further its appeal.

I actually really hope that both games (GT5 and Reach) come out this year because it will then make people realise just how big Halo is. The last proper GT game sold 2.4m in its 1st week, the last proper Halo game sold nearly 4m copies in its 1st week. It would be good to see this match up happen.
For GT5 to beat Halo it must basically triple the sales of the best selling PS3 exclusive (Metal Gear Solid). To put that in further perspective, Halo ODST (which i hated with a passion) outsold MGS4 by over a million units in just 3 months.

Halo Reach will kill GT5 sales

Opening weeks for Halo are usually large...but I honestly do not believe this halo will sell as good as previous ones. I have multiple friends who play/have 360, and they have always gotten halo first week. They say they aren't even going to get this one because MW2 and BFBC2 are already way better than Reach will ever be. It will be something on the Wii for sure, otherwise GT5.

Halo: Reach won't sell 10 million though.  Halo 1 and 2 had very very limited competition.  Now, you have Call of Duty and Battlefield along with some other smaller games.  I will wager that Halo Reach will have lifetime sales of only 8 million, opening week in the 3's.  Gran Turismo 5, however, has no games even close to it on the ps3.  The prologue which was very few tracks and cars sold 3.65 million.  GT5 will sell in the 2's for opening week, have huge legs to carry it on, and as long as it releases aroudn the same time as Halo: Reach, will beat Halo: Reach for the year.

Halo Reach does 6.5 million in week one, and quiets the crowd!

baal its almost guaranteed halo reach will have 10mil lifetime unless the new xbox comes out like a 6 months after reach. MW2 is getting old for most people. Battlefield will become old by the time reach comes out. They really should have added a forge like mode to battlefield. =/ would have made the game have unlimited replayability like halo. Expect microsoft to spend more money advertising the game then it probably costs to make it XD. I don't see why people who think gt5 will destroy its sales point to odst sales but ignore prologue sales. Both only show how strong the brands still are. They outsold almost every critically acclaimed game on both systems while being considered mediocre and not worth the full price.