Second Runner Up: Doom
Doom is one of two particular FPS titles this year that helped make the single player campaign cool again. The grand daddy of the single player FPS experience came out of retirement to tell Call of Duty to get off its lawn and show the world how they used to do campaigns back in its day.
Combat is fast-paced and chaotic with a soundtrack that perfectly compliments the action. Weapons are varied, and most importantly fun to use; a crucial feather to have in your cap when your game is mostly about killing demons over and over again for hours on end. Maps have an old school feel to them, encouraging exploration instead of throwing you down a hallway filled with endless lines of enemies. Doom can get real old school on your ass, too, if you up the difficulty.
Somewhere along the line, FPS games became more about competition (which is cool too) instead of just being games you could enjoy alone. Doom reminded us that there were good FPS experiences before the internet, and you can still play one on your own today and have a good time.