It's one of the AC games which showcased a major leap in tech, with dense crowds powered by GPU-based skinning and its enhanced motion-matched animation tech.
I was blown away with the graphics and gameplay during their initial Notre Dame demo, with the game featuring a lot of buildings with navigable interiors, good long-run parkour lines. The Co-op trailer was also badass. The phantom blade was one of a kind.
In general, a forgotten but good game.