“The Orange Box”: Four years later, each game in the dreadfully named “Orange Box” has graduated to becoming legends in their own right. “Half-Life 2: Episode Two” was the last the world has seen of Gordon Freeman, and he has yet to reappear. “Team Fortress 2” has gone from elegant class-based shooter to war-themed hat simulator. And of course, the little experiment known as “Portal” now has a full-blown sequel, already one of the finest games of the year.

“Halo 3”: Master Chief’s first foray into the then-next generation marked the end of Master Chief’s story. It had everything a fan could want, from a four-player co-op campaign to an absurd number of gametypes in multiplayer. For good measure, Bungie even let players edit maps with the Forge tool. The developers have since bid farewell to the series with “Halo: Reach.”

“Call of Duty 4: Modern Warfare”: Three “Call of Duty” games later, the tightly scripted but intensely cinematic campaign of “Modern Warfare” is widely regarded as the best in the series. The multiplayer structure was very influential—its system of unlocks, perks and everything in between is now the standard for all multiplayer shooters. “Call of Duty 4” turned a popular series into a perennial juggernaut. With “Call of Duty 8” on the horizon, things are unlikely to change any time soon.

“Bioshock”: Ken Levine’s brainchild, a twisted tale of utopia gone wrong, remains a masterpiece in imagination. It introduced us to now-iconic characters such as Andrew Ryan, Big Daddies and Little Sisters. Rapture, an Art Deco inspired underwater city, remains one of the most brilliant and well-realized environments in any medium. Since then, few games have managed to evoke the sense of raw wonder of “Bioshock.”