Example, I believe Assassins Creed Black Flag is the best in the series instead of AC2. It has awesome progression, exploration, naval combat and stealth. Assassins Creed 2 was good, and it was my second game I played in the series but I never got as attached to is as 2.
Imo Ac3 was better than Black Flag, though I enjoyed 1, 2, 2.5, 3, and Black Flag. The game was fun, but the story sucked, and the outside the animus stuff sucked as well. The series completely fell off narratively after 3, and fell off the cliff after Black Flag