Ever since Rockstar broke the mould with the unbelievably influential GTA III, every idea within has been extrapolated out in a million directions. Mostly that's meant scattering your quest-markers across a hugely expansive world for the sake of it, but it takes real skill and a perfect sense of immersion to make the most of what the genre can really offer. That said, what makes you class something as a truly brilliant open-world game? One that makes the most of its setting and layout to get across the sensation that you really are moving through an entire world of content? Which games had the most vibrant cityscapes, most well-designed fiction and most robust character-sets that felt as though they were going about their business as you were yours? In short, which open-world titles by genre transcended the label into being portals into their respective universes, with all the trimmings that come alongside? Rockstar have certainly continued to iterate on their cast-iron template, slotting things of varying importance in and removing others along the way - but the fact remains that like almost every artistic endeavour; the people who get there first are rarely those who stay on top as years of competition-bred innovation overtakes them. So, with GTA III launching in 2001 and marking the turning point of the century in more ways than one, which developers applied everything about its design to their own properties the best?