4. Spore

Development begun: 2000

Released: 2008 

Sims creator Will Wright originally envisioned Spore as SimEverything, and that's what it was called upon its announcement in 2000. Although the name changed, Wright's lofty ambitions for the game didn't. Unfortunately, his vision was a little too ambitious, since what ended up coming out—eight years later—was used by many gamers as little more than a glorified character creation engine.

It received decent reviews, but ultimately didn't live up to the expectations built over nearly a decade of development, not to mention Wright's exaggerated and, frankly, unrealistic vision of the god game to end all god games.