This very much depends on the kind of game you want to make, too. I would not suggest to create a city for a 1st person perspective with blocks but an isometric game like Syndicate is perfectly fine to do so.
You can use blocks with default/ simple testing textures to create the layout easily and test the gameplay and make changes if necessary. If you are pleased with the level sketch you can add details with blocks and models or use the layout for basis in Blender or any other program.