Should I nominate the Star Wars: Knights of the Old Republic games as a series, then? They are in continuity with each other and there's a few party members the same between the two, and various characters from the first who pop up for cameos in the second. On the other hand, they're from different developers and really quite different tonally.

(And I don't play it, but what about The Old Republic MMORPG? Same continuity but 500 years later. Should I be nominating under a tag broad enough to include that as well?)