AC1 had the best setting. But they didn't do much with it, which is a damn shame.
Seriously, I wish they'd revisit the Crusades, because not only is it an interesting time frame, there's also plenty of real history to build on, considering there was a real assassin order back then. Learning more about the Nizari Ismailis and the fida'i would be really cool... but who am I kidding, that would take a developer who wasn't as Casual as they come. Ubisoft's casualized so many series. Splinter Cell, Rainbow Six, Ghost Recon, the list goes on. I guess what I really want is some sort of a CD Projekt Red/Bioware/Assassin's Creed mix of the Crusades.