Well get Assasins Creed. Though the game play is repetitive but still the amazing graphics and sharp textures and a decent story make you forget that. I see it as a Medieval Hitman game, speaking of which you could try Hitman 4 might be a little old but its awesome. I think these two might be multi-platform so if you want exclusives I'd recommend Halo 3, Gears 2. And you might wanna try Fable 2, i haven't played it yet but have heard that its pretty cool.