Hmm... Halo 3 without question will get there, making it one. Unfortunately, as I see it, it will be the only one. COD:MW will come close, I'll guess ending around 9-9.5m. I see a small surge from MW2 and a moderate one from the platinum rerelease, but neither of these have a history of letting the games fly up the charts for an extended period of time. If there is a second one, though, I do see it being MW1. I do not think MW2 will do as well as 1.
Regarding other games mentioned, Reach is out for not having the fanbase. Future announced Halo games are still spinoffs, which after Halo Wars probably not being what some people expected, will make those people cautious of any non-numbered spinoff. 5 million, sure, but not 10. Halo 4, though, will come out too late in the gen to see 10 million total. Don't get me wrong, it'll have an excellent release, but too short a lifespan to get that 10m.
-dunno001
-On a quest for the truly perfect game; I don't think it exists...
