Play the first two. The gameplay isn't like any other game you've played before, I can promise you that. It's very hard to get used to, and the second game even differs hugely from the first. But that trailer didn't even totally cover what it is. It's an RPG. You're a monster hunter, but you also make decisions. And unlike in games like Mass Effect or any other RPG around, there is no good or bad choice. There is a bad choice and a worse choice. There is no white and black, only shades of gray. And that is the most interesting thing I've seen in an RPG because it means you seriously think of your choices. I cannot stress that enough. Play the first games- I highly recommend them. They're cheap too.