5. BioShock (2007)
Word to Ken Levine, BioShock's enthralling story—about a man who finds himself fighting his way through a beautifully creepy underwater dystopia while saving (or for more malevolent-minded players, harvesting) little girls for chemical currency called ADAM—blew the doors open. Not just on FPS mechanics, but also, with regards to how storytelling can alter the impact of a video game, and especially, a first-person shooter with a voiceless protagonist. Of course, adding 40s-era guns and combat-altering Plasmids helped enormously. What's more fun than shocking your enemies with lightening? Blasting them with water to electrocute them as you do it. The moral, religious, social, and Ayn Rand-infused political components all added to the weight and heft of this now classic title.