Eh, agree to disagree circa 2005 ... absolutely nobody considered it on par with (Illinois') Assembly Hall or the Breslin Center simply because the crowds weren't nearly as rowdy during that era due to bad teams. Our full 2005 game there is on YouTube, and compare that environment (which included literally thousands of Illini fans because there were so many tickets available, FWIW...) with our 2005 home games in Champaign on YouTube. Mackey was not even close.
I am not saying Mackey wasn't an amazing atmosphere before that, in the 1990s or 1980s, for example, and I am not saying that it is not inherently set up to be a better homecourt advantage than SFC due to its construction, either. My point is rather just that we cannot truly judge a homecourt advantage while a program is down, and these things ebb and flow, and there have been times when we were up and they were down and nobody considered Mackey better than Assembly Hall/SFC. Programs like Purdue or Illinois that have been good historically tend to maintain at least a pretty good atmosphere even when we are down (we had several sellouts during the Groce years, for example), but both are still WAY better when we are good, as are all programs.
There is an alternate universe where Illinois football has averaged 9 wins per season over the last three decades, and teams are absolutely horrified to travel to Memorial Stadium with its iconic architecture, swirling wind tunnels and rowdy crowds.
For a hoops comparison, if Minnesota had our history in hoops and had our record over the last four seasons, we'd all be talking about how The Barn is possibly the coolest atmosphere in the conference.