This site, songkick, came up with a rating of the top cities for rock in the US: http://www.songkick.com/blog/2010/11/18/top-10-cities-for-live-rock-music/
Interesting, but I have issues with what data they chose to go on: rock shows per capita.
???
A lot of shows relative to the population means... sparsely populated shows. That's the only logical conclusion I can come to. And that equals a "top" city for live rock? And "top" = "best"? I disagree. Square footage per show does not equal quality.
On top of that, I just don't believe that Madison WI has "hundreds" of music venues. (I lived there for 5 years, though granted, that was ~10 years ago.) And a quick search for live music shows of any genre in the Madison weekly, the Isthmus, shows them to have 56 on a Friday night. So they probably have around that many venues. Not 4x that many.
Pretty charts, but some data-driven approaches just fail.