Counter-Strike: Condition Zero

In 40 libraries here. 9 launched it, and the typical player put in 1.4 h. 1 finished it.

The main story is about 2 evenings of two hours, or 6 with the extras.

Named in 0.8% of Name 100 runs, about 1 in 130: people remember it when asked to name 100 games from memory.