HL2 was a more expansive game that had more ideas. In that sense it's really a far superior game. I absolutely hate the way they paced it, running each successive gimmick or gameplay type into the ground before moving on, but there was actually a lot of variety there, and the game was pretty robust if you look at it in total. FEAR, by contrast, did one thing and did it well, and that was about it, and it also lacked the variety of locales that HL2 boasted. Most hated that, though I actually liked how real it felt. That lent it some weight, in my mind. But where HL2 really failed, pacing aside, was story. The story was lame enough by itself, if you can even call it story (I've gone over that a billion times), but the presentation just wasn't believable. Others will of course disagree, but I thought FEAR did the silent protagonist thing much more convincingly. For a game that technically had less story and wasn't really even striving for story excellence, I cared much more about the people there than I ever did about anyone in HL2, including Gordon and Alyx. That had everything to do with believability. HL2 had no believable threads whatsoever. People treated Gordon like a god for no reason, and the interactions didn't make sense without two-sided contact. FEAR, even with a premise equally outlandish, made sure to keep it grounded. That's where they really succeeded.
