Player housing is common. Player-built cities are not.
A personal house can be instanced, decorative or isolated from the wider game. A player city or settlement becomes part of the social world: groups organize construction, ownership, defenses, services, politics or territory around a shared location.
Darkfall’s clan holdings are a classic PvP-oriented version. Wurm Online takes a more constructive approach, with persistent deeds and communities that grow through terrain work, roads, buildings and long-term maintenance.
Other games blur the boundary. Some allow extensive free building without a formal city system; others provide predefined holdings that clans develop. The useful question is whether the settlement itself has persistent social or territorial meaning.
For players who care about communities, that distinction is often much more useful than a broad genre label.