I thought this was an interesting thread and might be worth reviving.
My wife and I stayed at the Renaissance Esmeralda a couple of months ago; we both agreed it was the best buffet we had been to at any hotel, Marriott or otherwise.
Other good ones:
Baltimore Marriott Waterfront
Minneapolis Marriott City Center
Monterey Marriott
We are staying at the Camelback in December for the first time; we will definitely have to try breakfast there. Have any Plats succeeded in getting breakfast comped at this property?