Different hallmarks for different parts of the genre. It's not as clear-cut that there is 1, big overarching game that defined it all.
There were multiple games that each added something to the table.
For example:
- Wolfenstein 3D put the genre on the map.
- Doom revolutionised level design.
- Quake made multi-player FPS a big thing.
- Half Life revolutionised storytelling.
- GoldenEye 007 defined console FPS'.
And one can go on listing games for being minor landmarks and perfecting certain things, like Halo really making console FPS popular, things like that.
Gabanuka said:
Doom for sure, it had everything modern FPSs do and more.
Que? Yeah I know what Doom did for the genre, but I'm not qúite sure about the latter part of your statement.