No offense, I'm skeptical of any "objectively great" discussion. But let's assume I agree with you on that, then I still think you're under-rating the importance of Garth Brooks. While country had a little bit of a surge in the late 70's, with Dolly Parton, Glen Campbell and Kenny Rogers having cross-over hits, by the early to mid 80's, country was a dead issue beyond the core fanbase. Garth's debut was in '89, and even though Shania Twain gets mentioned here, her first album with Mutt Lange wasn't until 1995, and by then, Garth had five or six records out (he was doing basically an album a year for the first few years).
He was touring arenas and stadiums on his own when most country artists were struggling to fill 3,000 seat theaters as part of a package tour or as opening acts. I don't know about where you live, but here, in the States, the "Country Music Awards" is a prime time, major network show, rivalling the Oscars and the Grammys.