This plugin gives you the ability to display most commented posts on the entire network, using a specific shorcode in posts or pages, or using the widget dedicated to this.
Shortcode example:
[wp_mpp max=5 type=ever show_posts=0 show_comments=1]
Use following shortcode parameters:

• max : maxium entries to show
• type :
  • ever : all time stat
  • lastmonth : last 30 days
  • currentmonth : current month
  • lastweek : last 7 days
  • currentweek : this week
• show_posts : display (1) or not (0) total number of posts published accross network
• show_comments : display (1) or not (0) total number of coments for each posts in list.