Los Angeles is amazing for helicopters. Most of the higher buildings have helipads, and the photogrammetry is so good they are useable for landing even without addons.
Tokyo is very similar, excellent photogrammetry and lots of helipads on the higher buildings. Seems they are not actually used in real life, but only designed for emergencies. Again you cannot start on these helipads, but landing and then taking off again works just fine.
Third favorite for me is the freeware Return To Misty Moorings scenery pack in Alaska. So many lighthouses with helipads, and cabins where you need to find a suitable spot to land close by. Or you take a helicopter with floats like the freeware R44.