I had a very nice stay this summer at the Méridien National. Upgraded to a small, but lovely, junior suite. Did not have a Kremlin view, but had one from the breakfast dining room (included in my rate). The breakfast was one of the finest anywhere (fabulous pastries). The location is perhaps the best in Moscow. Service was very friendly. Highly recommended.
I stayed at the Sheraton a few years ago and definitely not as luxurious as the Méridien. As I remember the walk is about 20 -30 minutes but YMMV.