The only FPS'es I used to play are the one produced by Monolith studios (If I remember the name correctly).
* Blood 2 - The Chosen was so cheesy, badass, and Uwe Boll-esque that you end up liking it.
* SHOGO : Great story, gameplay alternates between on-foot missions and ones on a mechanized unit. Story follows the MGS scheme with lots of betrayals and plot twists.
As for multiplayer games, Outlaws was the shit. First Person Shooters were good 10 years ago. Now, I wouldn't touch anything but Metal Gear Solid and Final Fantasy games, If I have the time.