Out of those games, Alan wake is the only one I haven't played. I have to agree with them though, I found Dead Space 2 scarier than Condemned and RE5.
Although there results aren't really well done. For instance, I found Dead Space scarier than Dead Space 2, but they haven't included that game in testing. Another thing is that they have only tested it on 6 people, which obviously isn't good enough to "Declare Dead Space 2 Scariest 360 Game.
They need to include MANY more people and A LOT more games before I can take this seriously.
EDIT: Also, why are loads of people bringing up Amnesia? It isn't a 360 game, and the title clearly says "Scariest 360 Game".
EDIT 2: Looking at my games list, I have F.E.A.R 2 on the PS3 (but you can get it for the Xbox 360), and in my opinion, that was much scarier than all those other games on the list combined.