People, don't ever claim to be an expert unless you know the genres entire history, and have played the games that created new plateaus for fps development.
Doom started it, while it wasn't the first, it was the first fps to become popular enough to float a sequel.
System shock 1/2 expanded the genre to include elements from other genres, making greater depth of play possible. Half life eclipsed this series with a massive advertising drive, becoming the standard for some time.
A hundred water-weak copycats sprang up to dilute the genre further, like heretic, wolfentstein, halo and others, leading to a regression in gameplay; back to Doom's corridor shooter style.
This continued for a long time, with only minor improvements.
Then along came Deus Ex, which was strongly reminiscent of system shock, and brought new elements to the table.
Then bioshock/dead space, and slowly the "vanilla shooter", corridor shooter style is dying out and is being replaced by the hybrid style, and stuff like TF2/L4D.
Anything I missed?