3to1 or 2to1 I'd say 1.5to1. Why? Look at the Darkness.
EDIT: I want to point out the Darkness is 2:1. However we have to rember 2 things. The loyal Sony players, are normally not the FPS addicts the 360 guys are. Also, you factor in This is StarBreeze's second game, second for microsoft, first for sony. No-one knows who they are, what they do, how they work. Quite a few of the sony guys were actually TRASH talking The Darkness. I put them in their place, and then they rented it, and stuck their foot in their mouth. Also, the die-hard FPS people for the PS3, also had to choke on Rainbow Six: Vegas. So that took from sales of Darkness. I say 1.5 to 1 is accurate.
EDIT2: OMFG OVERLORD IS OUT! YAY! That game is gonna kickASS... IGN castrated it wtf. lol. IGN less than 7. IGNEurope gave it a 8.1 Oh well, I read a review that said you can piss on carpets... sounds kickass to me.