I did start such a thread for Hyatt a few years ago. Predictably it remained short. Today, I can think of three Hyatts: GH HK (Ruinart all day), GH Tokyo (Veuve Cliquot) and GH Fukuoka (which used to have a 4-day rotation of champagnes, but now has cheaper stuff out, Chandon Australia, with individual glasses of Champagne still brought out from the back for regulars).

As for Marriott, I pretty much reduced my stays to zero, relying on LT Tit status occasionally when Marriott is the only/best option. Haven't seen much champagne at all over the years (and as you say RC obviously shouldn't be included in this comparison, because you don't get free access to those lounges as a mere mortal). Hermitage Gantois in Lille has a bottle of champagne out for breakfast, but that's all I can think of when it comes to champagne at Marriotts.