Left 4 Dead
Sure, technically Valve has sort of (kind of) continued to update Left 4 Dead 2, sometimes with the help of fans, but I still consider this franchise dead, like most other Valve franchises. Which is sad, because Left 4 Dead ruled.
Valve did what Valve does best, and crafted two online co-op shooters that were perfect to play. Shooting down hordes of zombies with friends or hunting down other players as a special infected was a blast. Even if you played online without a mic, Valve built L4D1 and its sequel in a way that made it totally possible to play without talking. (Though chatting did help!) It also crafted characters, like Zoey and Ellis, that people cared about. I still think about Bill sacrificing himself in the final L4D1 DLC to this day. Hopefully, someone else at Valve is also thinking about Left 4 Dead. I hope so, because this franchise and its fans deserve a third entry. — Zack Zwiezen