I get scared in an adrenalin pumping way with HL1, i was scared when i had low hp in We Got Hostiles and I first saw the hecu and i was pinned in the place where the osprey kept sending marines down infinately.
Certain elements of hl2 creep me out like the radio1.mp3 song, when i heard it, found the tv and it broke when i moved near, then the civ later on whistles it. Also the children screaming in the playground when pickign up the doll, scared me silly.
The HL2 beta had a gman sighting that was scary, i saw it on youtube.
So I’d expect Black Mesa to be at the level of half-life with emotion, nothing creepy like HL2, perhaps the gman sightings will be creepier in Black Mesa, like in Unforeseen Consequences when gman is behind the door, maybe the lightswitch could flicker or something and illuminate his face in a scary way.