I think you can call out examples of MO, SR, 4S and Waldorf Astoria properties which are far from luxurious. To me IC seems on a par with Starwoods SR and/or Luxury Collection chains, with WA, 4S and similar to with Starwood for Marriott some sort if hybrid of JW and RC.

I think the individual IC's are far more variable than perhaps their near cousins in other chains which makes direct comparison somewhat variable. Looking at the IC London Park Lane I would happily put it on a par with almost all other Mayfair luxury hotels. The IC Westminster in the same city Is less luxurious and could equally be a JW Marriott or Conrad.

IC does however tend to offer more relevant luxury to my needs with more emphasis on discreet attentive service and less on pointless "butler" services.