@ Soriku

Remember that MGS3 came late in the PS2's life-span, and most of those 120 million owners either moved on, or had a defective console. (Edit: Also had stiff competition in late '04)

Also remember that this is being marketed, and obviously so, as the finale of MGS. And with MGS being one of the more recognizable franchises in gaming, people are going to want to see the finale.

I actually wouldn't be surprised to see MGS4 sell more than the previous iterations.
Especially if the PS3 can take off in '08.

Hot shots golf only did like 1/3 of what past games did in japan... i dont think this game will reach 3 million to be honest.

I'd say,

Bombed = sales of less than 1.5M to 2M

Average = 2M to 3M

Great = sales > 3M

Edit: Adjusted numbers 

True =P.

But from what I've read from interviews with Ryan Payton, and Kojima himself, is that this is indeed the end of Solid's story. No tricks or suprises, just resolution. 

the thing that kills me about this whole MGS4 going to xbox 360 that i don't think most x360 owners really want to play it. i guess admitting that a console you don't own has games worth playing is asking too much out of some people.

MGS4 sales expectations:

2008 year
2.0million
lifetime:
2.6million

Meh, Starcraft, Neos and I know better :).