Why would you say that Assassin's Creed was more hardcore than core?
Nothing sells big by selling mainly to the hardcore. The hardcore are a small percentage of the core, what makes them important to publishers is that they buy a lot more games generally, but there's not enough of them to make games sell multi millions.
A game I'm developing with some friends:
www.xnagg.com/zombieasteroids/publish.htm
It is largely a technical exercise but feedback is appreciated.