Yes

MW2 - ~13.5-14m
Halo 3 - ~12.5-13m

There is no time for it to catch Halo 3...Halo Reach will be out next year, and that will sap sales of MW2, in addition, a new COD will be out next year as well...

ODST and WaW didn't stop CoD4 from selling.

Infact, in the 10 weeks up to MW2 release CoD4 sold ~200k on the 360 alone. WaW did ~130k.

Reach will not hinder MW2, in fact any shooter is not going to hinder the sales of any other shooter.

Why do people have this "thing" where people can only buy one shooter!!!

Mw had an 80% drop off, much bigger than Halo 3 if I remember. so we'll see how legs go. Just because COD4 had great legs doesn't mean this game will.

not a chance

Why would they have?  We are talking about a year from now...and it's a matter of supply and demand.  The used game marketplace, along with other big shooter releases will have an impact on MW2's legs.  How many copies of Halo 3 sold in that 10 week period? 

Can it? Yes. I don't think it will outleg Halo 3 though.

no because activision will will release a another game that will stump its sales next year. also mw3 might be out in another 2 years.

Halo 3 has that advantage that couple million of its sales has been from bundles. It will be tight race. Both will end up with over 12 million sales imo.

It's a legs issue, indeed.  Sales dropped 80% this week (projected), which isn't bad, considering week one, but it's looking like maybe 7 million by year's end...then it's the Bataan death march to 10 million+.  That's not as easy as it seems...but it depends on alot of different factors, such as what other software options are out there.