For me, it's Bioshock, no contest.
From its amazing atmosphere and setting, to its awesome Plasmid-powered combat, to its strong story and characters, to its stunning audio-visual presentation, it ranks as not only the top FPS games of its decade, but for me one of the greatest games of all time.
Honourable mentions to Halo 1 & 2, and Call of Duty Modern Warfare & World at War.
Last edited by curl-6 - on 06 June 2019