I think well-lit environments would be good in a horror game used as frequently as dark areas. It lulls you into a false sense of security to be able to see everything around you. Then something absolutely petrifying appears in the middle of a brightly-lit room and any feeling of security you may previously have had is shattered. Humans are born with a fear of the unknown, however dormant it may be in some of us, which makes dark areas so creepy: "if I can't see what's lurking in that half-opened closet, it must be terrifying."