Half-Life 2, since I don't count Deus Ex as an FPS.
Crysis would get a vote near the top as well - heavily underrated for the most part.
PlasmaFrog said:
The term "Best Ever" is used too often and will lose its credibility due to it being a subjective topic. There isn't an absolute best. You should use a phrase such as "In your opinion" or "Your Favorite" due to the individuality of the subject and opinion.
Or he could just assume that we're all inteligent enough to work that out for ourselves, and that of course this isn't an objective topic.
Which we are, and which he did.