All of these bands are roughly from the same time too...60's-70's music. You can't pin point the greatest band ever period, especially out of two decades.
These are all great great bands, but it's true they're limited to the 60's and 70's rock... plus you forgot Black Sabbath!!!
Everybody likes New Kids on the Block. *sings* I got the right stuff. Baby. Love the way you turn me on.