REM, The Smiths, The Pixies, The Cure, Husker Du were all good bands, but not mainstream like John was.
Maybe REM in the 90's, and the Cure a little bit, but they were no where near as famous as Lennon was.
So many things to say.
I'm very impressed that only nine months into the eighties Lennon managed to produce the pinnacle of that decade's mainstream rock.
Prior to John's death Double Fantasy failed to make even the top ten in the UK or the US and was sliding down the charts. This makes it unclear that whether prior to MDC's intervention the world at large regarded that any pinnacle was being reached, or indeed whether Lennon was particularly popular.
Elvis was an exceptionally popular artist in the seventies (maybe the most successful solo act in terms of chart action?? ), mostly propelled by renewed interest following his untimely death. Does this then mean that some of his seventies work is the pinnacle of that decade's music?
Mind you, isn't eighties mainstream music generally regarded as bland, overly slick, soulless radio fodder, generally regarded as the nadir of rock's short life? In that case you may have a point, though I'm not sure that being top of that rather turgid pile is something John would have been particularly proud.