5. Grand Theft Auto III
If we're talking about a franchise's legend and mark left behind on an industry, you have to go back past Vice City and San Andreas, right back to when Rockstar first dropped GTA III out of nowhere and went "Look! Look what we've made!" The resulting wave of expectation-shattering review scores and consumer reaction was unprecedented, and remains something you were either slap-bang in the middle of at the time, or have read about in abundance since. GTA III literally changed the world, inventing and perfecting the open-world genre right off the bat. It let you tackle missions however you liked, encouraged exploration through the placement of random stunt ramps dotted around Liberty City, and had missions that could be immensely difficult, the completion of which would then unlock more of the environment. 15 years on, GTA III still feels like stepping into another world, its lonely stretches of road at night having just the right amount of ambiance to make it truly timeless.