City 17's filth and oppression create an Orwellian sci-fi setting worthy of its own spot on any Best Worlds list. Half-Life helped itself. Gordon Freeman escapes City 17 for the haunting, abandoned Ravenholm, returns to take down the alien Citadel, and eventually escapes again to the scenic, almost peaceful White Forest. Mind you, this all happens after the Black Mesa research facility, one of modern gaming's most memorable places. Combined, the Half-Life universe encapsulates the best of sci-fi, literature, and film. The Combine is a menacing force, and worn down a familiar place nobody wants to be part of anymore. Half-Life also features a distinct aesthetic and an original, interesting world to be part of. What's more, the Half-Life universe becomes an entirely different beast when taking Portal into account. The levity of its bleak situations, lovable and telling guides, and expansive set of stuff to accidentally discover bring an already amazing world to peerless status. Plus there's a pretty cool robot dog.