GTA 3 created the modern GTA template: three boroughs, unlocked gradually, in a full 3D city. Twenty-five years later, you can still see it in what GTA 6 is doing.
Three boroughs, gated unlock
Portland, Staunton Island, Shoreside Vale - unlocked as the story progresses. It invented the progression-as-map-reveal gameplay GTA games still use.
Each borough had its own look - Portland was gritty, Staunton Island was commercial, Shoreside Vale looked fancy. The trend of making regions feel like characters began.
What GTA 3 set up for everything after
An open-world city you roam as the story unfolds. Each district has its own feel. Vehicle-based missions. Pedestrian numbers (low by 2026 standards, revolutionary in 2001).
Vice City and San Andreas would take this concept further. GTA 6 remains within the GTA 3 template, just massively scaled up.