Probably one of the best sequels I've ever played. It does everything you want it to coming from the first game and the story is without a doubt my favourite in the franchise. Everything from characters to areas feels memorable and the modern day plot is still well handled.
Despite all this, it's not exactly a masterpiece and still suffers from some clunky gameplay in combat and climbing. As well as this, the final story beats fall more flat from forcing the player to go collectable hunting to progress to the end.
Generally though, I always have a great time with AC2 and can always find more to love than not.