I always stay at The Ritz Carleton in SF whenever I am visiting or doing a staycation. The rooms are always clean, well maintained. The service is simply top notch, from the checkin to room service to restaurant service, I have never seen better service in any hotel in the city.
The restaurants have great food, great drinks, the location is ideal for exploring the union square and chinatown areas but is also walkable to areas like Russian Hill, Embarcadero etc making it a perfect spot for travelers. But if I have to pick one reason I keep coming back to this hotel, it has to be their incredible service