Well not really unique, but though it had a very nice flashbacky feel it still had some differences. For one you could divide much of the game into smaller "levels" which were each a kind of puzzle. In flashback everything except your enemies and that one VIP was static. Here you need the others to help you do stuff, and abe's exoddus you had to have many more to follow you.
As for Resident evil. That was a fairly nice game too though it resembled Alone in the dark a whole bit.