Poor Marketing - Many average players have never heard of it.
Unexciting title - It's an unknown name to players.
That being said I don't think the sales of the game are going to be that bad. If the pre-order charts are right it should be good for 150k-200k sales in America this week. European sales shouldn't be to bad this week either considering it only had a couple days worth of sales there.
It could be a case where word of mouth keeps it going for a while. It's a fantastic game, hopefully sells well.







