When it comes to its appetite for innovation, the games business is cyclical. When it's at its most risk-averse, the big publishers seem loathe to bet on anything but a sure thing. See: the proliferation of military shooters in the 2000's taking aim at Call of Duty's world-bestriding success and never quite succeeding, or our current day's obsession with the open-world game, all in the hopes of seizing a Grand Theft Auto-sized hit. As anyone who's paying attention knows, though, today's surefire hits were more often than not yesterday's oddball, innovative gambles.
You can almost read the contents of this list as collective blueprint for the biggest games today. Some were immediate hits and changed the course of games; others pointed the way toward ambitious designs that were just ever-so-slightly out of their reach. Regardless, they all made an impact, and today's designers owe them a debt of gratitude.