If I absolutely had to pick one and only one, I’d go with AC2. It’s “most like” a kinder, gentler, fleshed-out and modernized AC2.

It has aspects of WoW (much of WoW was taken directly from AC2, though, so there!) such as quest-givers with icons over their heads, and (over)using the same mob types. I also see the Deed system being similar to the Title system of Guild Wars only taken to the next step, just like WAR will be cranking it to eleven with its Tome of Knowledge. I could also relate it to Vanguard as both attempt to balance solo and group play throughout the entire leveling game. The player housing I see as a compromise between SWG and EQ2, a full public neighborhood but instanced from the world.

I’m curious.