The feelings towards hotels are completely subjective and unfortunately people here often don't understand IHG's business model in which all the hotels are independently owned and subject to brand standards which are not measured on subjective appeal. Hotels cost a fortune to own and run and to renovate and they get old quickly.
I have stayed in Holiday Inns (e.g. Manchester City Centre) which are far better than nearby Crowne Plaza (Manchester City Centre)... meanwhile the Crowne Plaza Marlow is a lovely hotel which has been recently refreshed, whilst a number of Holiday Inns which were old Crest / Forte hotels in the UK are decidedly ropey (IMHO)
Meanwhile Indigos can be amazing - Paris Opera is an example, as well as several across the UK. The European Kimptons are excellent (in my opinion again)
Most IHG hotels in the US (new or not) are simply not as good as European ones in my experience...