Bear in mind that 4* hotels in Tokyo will often have service that is better than 5* hotels in many other parts of the world. Dated room styling and decor may be the main issue in older hotels. The Imperial, as mentioned by Pickles, is a good example of that, as is the Okura.

I would disqualify the Grand Hyatt from a 5* rating primarily because half of the rooms face the Mori office highrise maybe 20 meters away, requiring room curtains closed for privacy. If you get a room on the other side of the hotel, it might qualify.

I would also disquality the Westin because I find the decor overly ornate, indeed, over the top, although I notice the lobby is a bit more conservative than it was during the days when I used to stay there.