Fable II is absolutely a system seller in the sense that it is an excusive next-gen premier for a successful franchise so many fans of the series who have not purchased a system will see fit to do so.
However, it is not quite as big a system seller as Halo 3 or Metal Gear Solid 4 because of the fact that Fable, while being a relatively big franchise, isn't a HUGE franchise like Halo or Metal Gear and the fact that many WRPG fans have already purchased a 360 for Mass Effect. Furthermore, it is getting released around the same time as Fallout 3 which is another next-gen premier for a successful franchise so that will also hurt its sales a tiny bit.
Overall, Fable II will make good bump in 360 hardware sales (Not that we'll be able to notice it due to the price-cut/holiday sales increase) but it won't make a clear spike like with Metal Gear Solid 4 or Grand Theft Auto IV.







