This is one of my favorite new series to emerge this generation. The combination of conspiracy storyline, amazingly realized historical environments, and general bad-assery is a winner.
The fact that this game was released just a year after the excellent Assassin's creed 2, and yet improved on its predecessor in almost every way is astounding. It also added the most original and compelling multiplayer systems in years. Far from the cash-in that everyone assumed this would be, it further developed the characters and story in both the present day, and in renaissance Rome.
As a complete package, it's impossible to resist this game, and I can't wait to see where they take us next.