I will say this as someone who is a little down on AAA in general and Ubisoft, EA and Activision more than most. I loathe Ubi's generic sandbox games/AssCreed nonsense. That said, I adored this game. CoJ: Gunslinger, I thought was absolutely brilliant. I would have even played a longer version, though the 6-10ish hours is still fine.
I think i particularly loved the Unreliable Narrator storytelling. As a framing device it worked so damn well. It delivered the story wonderfully and worked hand in hand with gameplay and the art style. I haven't seen something so good since Prince of Persia: Sands of Time. The gunplay was great fun, I loved the level design, I loved that we got to visit all the Western mainstays...train, mine, saloon, town, wilderness. It had other cowboys, gunslingers, red indians, cards, whiskey, outlaws, lawmen, etc.
This game is a joy to a play. I thought it was a wonderful experience that I enjoyed more than I expected, had a great storytelling method that blended voice acting, art, gameplay and world building together. Not that long, hit a lot of high notes, want more of it!