Team Fortress revolutionized the FPS, inventing the headshot and the player class.
While I loved TF it was hardly a popular game and I wouldn't go so far as to say it revolutionized the FPS. I could be wrong but I'm pretty sure they didn't invent the headshot though they could very well have invented classes.
Counter Strike revolutionized the FPS, and has been the face of FPS for many years, until...
How exactly did CS revolutionize FPS? It was a great game but it didn't exactly change anything about the genre
Call of Duty revolutionized the FPS, introducing experience, levels, perk and weapon customization to the FPS.
I'm almost positive they weren't the first FPS to use experience or levels. Perks are just like abilities which have been in other games. Weapon customization has been in others, but not to the point CoD brought.