This should be a close one barring any major adjustments.

As of 3/20

MW2: 10.12M

Halo 3: 10.88m

The last few weeks MW2 has been selling about 85-90k a week while Halo 3 about 11-12k.  If both games keep up that pace, they should both hit 11M in about 10-11 weeks. 

unless either gets a bump or drops off, then it will be around the same time

whether MW2 can outsell Halo 3 is another question, I think it probably will eventually.

At this point it's not a matter of if, it's a question of when.  Halo 3 is already 30 bucks, MW2 is full price and outselling Halo by 75k a week.  There's still the inevitable GOTY edition and eventual price cut as well.  I predict MW2 will pass Halo 3 by the end of July if not sooner. 

I think Halo 3 will get to 11M first though, it's probably going to stay steady at 10-12k a week while MW2 will probably drop a little more before stabilizing. 

I think they will hit 11 million around the same time.

mw2 will outsell it but its not selling full price. Theres been so different deals that for the past 2 months the average price has been 40-50$ I think halo 3 will hit the 11mil first. MW 2 will sell much higher though. Lifetime of 14-15mil is very possible

this

Halo 3 I think, MW2's sales will drop a lit in the coming weeks imo

Halo 3, the beta for Reach ought to help and the MW2 sales are always slowing down.

Modern Warfare 2.

Modern Warfare 2 most likely