For me, it’s hard to top Paragon City from the MMO City of Heroes (RIP). Honestly, nothing has topped it for me since.
Why? It’s simple really - scale. Or, more specifically, the things the scale allowed them to do. By making the entire game world of an MMO a single city, it was allowed to feel like a city.
Atlas Park wasn’t just city hall - it was expensive fashion boutiques, towering office buildings, fancy hotels and emergency services all close at hand with the only ‘blue collar’ crime being relegated to back-alley muggings of city officials. King’s Row was packed dense with housing projects for low income families, but it was also where you found a lot of factories and Fifth Column rallies preying on the working class. And then, every now and then in King’s Row, you’d come across a small park packed between a tenement and a pipeline, and it felt like a city.
Size isn’t usually the most important factor in games, but the amount of personality and little details afforded to each district of Paragon City thanks to the sheer size of it did so much to make it feel like a place that you could go and visit, each subdivided zone being sizable enough to have a complex and distinct personality, and suffer from different villainous organizations often born from its demographics or pertinent issues. I truly hope to see another game like it in my lifetime!