How to create a module Dependency Graph? I am running a D7 site with 164 enabled modules. I need to create a module dependency graph so that I can get a better understanding of the module dependencies and find out which modules are critical. 

I have checked out https://drupal.org/project/drush_mm but the page says it is obsolete and not present for D7. 

Any alternatives?
There is the sandbox drush module dependency_analysis

It provides a drush command that produces a dependency graph using graphviz.  For me, I found that it was a simple matter of installing graphviz using homebrew:

$ brew install graphviz


And then follow the project page description.