50 Landmark Game Design Innovations
Next Generation has put together a lengthy list of landmark game design innovations that many of your favorite games probably wouldn't exist without. They break them out into self-contained units, though it's sometimes ambiguous how they're demarcating game design elements. Just the same, it's an interesting look at where game industry trends have led us: "23. Gestural interfaces. Many cultures imbue gestures with supernatural or symbolic power, from Catholics crossing themselves to the mudras of Hindu and Buddhist iconography. Magic is often invoked with gestures, too--that's part of what magic wands are for. The problem with a lot of videogame magic is that clicking icons and pushing buttons feels more technical than magical. The gestural interface is a comparatively recent invention that gives us a non-verbal, non-technical way to express ourselves. Best-known example: Wii controller. Probable first use: Black & White, 2001."
Come to think of it, I'm surprised "Freeform/Unending" like Elite hasn't been mentioned, seeing as it makes a point to differentiate them from Sandbox-mode games.