Since this is your bracket and idea, perhaps we need a little more guidance as to what would constitute the best. I was reading it as some combination of successful sales, originality and influence. Which is why to my thinking, Nirvana or Pearl Jam from the grunge/rock genre, Garth Brooks and Dr Dre would be the leaders in my mind. Other people can put those differently (Public Enemy or the Beastie Boys, Shania Twain and Metallica spring to mind) but that's how I would read the central conceit of this project. Which would mean that incredibly great bands who lack commercial success (and there have been a lot of those listed here) probably wouldn't even make the tournament. People on here love John Prine and wilco, but there's no way they have had the success commercially to even make a 32 team tournament I wouldn't think. But Define parameters as you see them. This is, after all, your show.