[KillerGremlin]

I went with Half-Life...that intro gave a tour of Black Mesa, and introduced players to what would eventually be total chaos. And it did it in real time with the player having full control of the Gordan. The entire opening sequence in Half-Life prior to all hell breaking loose is the most memorable FPS opening I can think of.

Obviously Half-Life hasn't aged well, but when you put time into perspective, I'm really surprised Bioshock is beating Half-Life. But I have a raging boner for nostalgia....so that's my bias.