I was at the Park Hyatt Ararat last month and would definitely agree with RussianGuy that this is the top property. (I also saw the Marriott and Kempinski, but Hyatt IMO is nicer with better location.) You are no more than a 5 minute walk from Kremlin, Red Square, GUM dept. store, etc., the hotel is new, the staff is extremely helpful, rooms are nice (but expensive), good restaurants, and good security. Like the other hotels, they also provide hotel car pickup at both airports (it's around $90.00 one-way from SVO, but worth it to avoid the hassle), and will provide you with a letter of invitation for your visa.