The first one, definitely. Serious mind fuck. Here's an example: you expect music to ratchet up and reach crescendo during a scare, right? And for the first half of the game, that;s exactly what happens. Then, for the second half, that still happens sometimes, but then, they also have music build, build build...and then nothing. Conversely, they'll also have scares happen with no musical cue at all. All of this leads to uncertainity of when things will happen, and therefore paranoia.
That's just an example, however. Most of the fear (c wat ah did thar?) comes from just a building sense of unease, built slightly by the aforementioned music. They managed to make you scared of normalcy and genuinely look forward to a tough fight. I have a distinct memory of when the tension got too much at a random time, and I just stood there looking at a random desk, terrified or no reason other than the excruciatingly built tension.
It might be worth mentioning, however, that that was my first horror game.
EDIT:
WanderFreak said:
Haven't played FEAR. FEAR 2 is not scary at all. The first few minutes, sure maybe a bit creepy with the movement in the corner of the eye, and quick flashes of things.
But half an hour later those movements in the corner of the eye and quick flashes of things are still happening.
Alma is the least efficient killer ghost thing ever.
Most people agree, the second wasn't scary at all. The first at least tried to be psychological and unpredictable about it.