Obsidian believe that New Vegas is the GTA: Vice City of the Fallout series.
Fallout: New Vegas' Project Director and Lead Designer Josh Sawyer made the comparison during a recent interview with GamingUnion. Responding to a question about New Vegas' use of the ageing Fallout 3 engine, Sawyer said:
"In many ways we've referred to it [Fallout: New Vegas] as the Vice City of the Fallout franchise. So it's really more focused on new content, new characters, and tweaks to gameplay, as opposed to completely reinventing what's already been done."
If New Vegas can make the same impact as Vice City, we're in for a rather nice ride.