When Assassins Creed first came out , I was very much excited about the franchisee. But after playing few hours into the game I was totally disappointed and I didn't finish the game. Eventually I sold the game!
Later I bought PS3 and subscribed to Gamefly. I rented out AC2 and though it was highly favoured by many websites I was cautious. And the game did justify the high ratings. Although it wasn't perfect as it should be, it was far better than the first edition.
And now I'm hooked up to the series completely. I finished AC:Brotherhood and already half way in AC Revelations.
I really don't remember which game improved so much in terms of game play, story, visual - in every department after the first game failed to capture my attention.