Cyberpunk 2077 is GTA 6's closest open-world city counterpart. The design philosophy is different, though.
Cyberpunk's approach
A city built up vertically. Tall and skinny metropolis. Megabuildings, skyscrapers and districts stacked on top of each other. The city's total area is smaller than GTA's. Streets seem never-ending because of the verticality, not the sprawl.
GTA 6's approach
A wider city sprawled out horizontally. Vice City is dense at street level but sprawls rather than stacking on top of itself like Night City.
Trailer footage implies that GTA 6 may have more pedestrians and cars at street level than Cyberpunk 2077.