Loved AC3, AC4 was...decent. Good looking, but lackluster in a lot of ways.
Wishing I had the money for 5, but sadly not.
Not surprised no one's heard of it, it seems like such a niche genre, and they seem to have no marketing budget. I never saw 4 until it was out, even though 3 was one of my favorite games at the time.
I blame complexity. The large number of stats seem to discourage people, even though you can ignore most of them unless you're really min-maxing. And of course the odd controls, has anyone seen a game with similar controls? It seems pretty unique, which is odd.