Titanfall, if its done right its pretty much the next call of duty. Plus it is releasing on 360 with 70m base.

*slaps allblue*

The OP said Xbox One ONLY!  Now, take that back.

Titanfall, because almost every XBox One owner will buy it, while Shadowfall will have to compete against CoD and BF4.

Killzone Shadow Fall.

my gut is saying titanfall but the numbers are saying KZ, aswell as TF being a MP only gaming

if i had to put money on it i would say TF will pass it in the long run

And titafall wont compete againts COD and BF4? 

I'll go out a limb and say that it does. 

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CoD and BF4 will be available in November - the same time as Shadowfall.  Titanfall will probably come out in March 2014, and I don't recall seeing any other FPS games releasing around that timeframe.  XBox One owners would have finished playing their launch games and they will be looking for something new.  Just like I see many PS4 owners picking up Second Son.

Killzone hands down.
- established franchise
- launch title
- bundled
- (probably) larger install base
- holiday release
- just look at the pre-orders

Titanfall will probably top killzone in total sales with all the 3 platforms combined, especially when it comes to the ps4

Hmmm hard to say I think it will all depend if the buzz for the ps4 translate in real sales, if the ps4 is beasting the X1 after launch I think KZ will sale a lot better but if they sale about the same amount of consoles Titan fall will sale a lot more than KZ I mean have you seen Titan fall