How are we quantifying this? Is it album sales, concert ticket sales. Or is it based on hoe many songs or albums charted within the top 100? Or is it just opinion?

I dig Nirvana and they definitely changed the face of rock forever. Given that Kurt unfortunately took his own life, the band never really got to see what their greatness could be. In my opinion the best thing Nirvana gave us was Dave Grohl. Whether you like the Foo Fighters or Dave or not, he has been the beacon of rock n roll and just going for it. His passion for music and his fearless approach and advocating for anyone to pick up an instrument, get with some friends in someone's garage and play no matter how much you might suck. Just do it and keep doing it. Have fun and you'll get better. That's what makes him great.

In my opinion there is no singular greatest band. Zeppelin are up there as are the Beatles. But so is Robert Johnson, James Brown, the Stones, Boston, Rush, Frank Zappa, Stevie Ray Vaughn, ZZ Top...