Retrospectively, it's very easy to say that only two specific game 'types' have ever pulled off the whole 'annual release schedule' thing.
Either a sports game like FIFA or WWE 2K (their team/roster updates necessitate regular releases) or Call of Duty, which uses Activision's substantial coffers and the same game engines on routine releases to make their deadlines. For Ubisoft though, despite having 10 separate studios working on AC at any given time, it was immediately clear even from AC Revelations that the franchise didn't need to be trotted out every year. I'll get to what that game did wrong in a later point, but despite closing off Ezio's story in an admittedly fantastic scene with Altair's corpse, the franchise steaming ahead for its 'proper third instalment' immediately felt tacked on.
It was Assassin's Creed III that was the first to release with a marked drop in quality. Texture bugs and graphical glitches abounded as despite a supremely slick opening Templar twist, every major character felt incredibly underwritten - not to mention the Homestead side missions were just pointless filler.
Not to mention, it was during AC III's shoddy launch window that we learned of the following year's instalment, Black Flag, once again hammering home that 'production line' feel that did a disservice to some otherwise solid narrative foundations.