Related: AC3 is pretty cool. It's got the least sort of "WHOA LOOK AT ALL THIS AWESOME ARCHITECTURE THAT I CAN PARKOUR ON IT'S SO PRETTY" stuff. The buildings you run on aren't even connected for the most part, and a lot of viewpoints are noticeably identical.
But in my opinion AC3 has the best story of an individual game in the series. So that's a thing.